When Savannah woke up on the morning of Oct. 25, 2015, she says she didn’t remember much of what happened the night before.

“My face was sunken in. I had bruise hickeys all down my neck. I just started crying, because I just felt so disgusted with myself,” Savannah, 17, told ABC News’ “20/20.”

Savannah, then 16, said she was disgusted because her Saturday night had been filled with beer, liquor and shots of Fireball Cinnamon Whisky.

“I felt like I was that drunk girl at the party, and I knew everyone was going to like, just you know, talk about it,” said Savannah.

That night, Savannah, her friends, and dozens of other students from Spanish Fort High School in Spanish Fort, Alabama, had attended an 18th birthday party for one of the Spanish Fort seniors. Savannah, a junior, was the new girl in class, having transferred to the school just a year earlier.

Watch the full story on ABC News' "20/20" TONIGHT at 10 p.m. ET.

Her parents, who were away for the weekend in New York City celebrating their wedding anniversary, almost didn’t give her permission to attend the party.

“For some reason I wanted her to stay home,” her mother, Emily, told “20/20,” though she eventually relented.

Savannah and her friend went to the house of Cameron Harrison, the running back for Spanish Fort High School’s football team, before the party.

“I knew of him. We had math together, but I had never, like, hung out with him or anything,” said Savannah.

The teens then headed to the birthday boy’s house, where Savannah estimated as many as 40 students gathered for the party. The 58-year-old grandmother of the birthday celebrant was home, but she was watching TV upstairs in her bedroom, emerging on occasion.

The teens drank whiskey, beer, wine coolers and other alcohol they had brought to the party, according to court documents and interviews given to "20/20." Savannah said she drank a large quantity of alcohol within a short amount of time.

“I had been to parties. I had drank, and I had been around alcohol but not to this level … I was just stupid. I wasn’t thinking of the consequences it would have on my body to do that,” she said.

Savannah said she remembered feeling dizzy but not much else.

“The last thing that I remember is standing in the kitchen with everybody singing, ‘Happy Birthday,’” she said. “It's like I wasn’t even in my body. It’s like my head was telling me like something’s not right, but I feel myself kind of fading out, like you know, from having control of myself.”

Savannah’s close friend, who asked that “20/20” call her "Jessica," said that it was visibly evident to her that Savannah had too much to drink.

“All of a sudden I see someone carrying her up the stairs. It was probably four people that were carrying her up the stairs, like she was a doll basically, like they just, like, each had like a limb. And I was like, ‘What the heck, when did this happen?’” Jessica told “20/20.”

Savannah’s friend, Taylor, who was one of the teens who helped carry Savannah, said they thought it was funny and that they did it so Savannah could lie in bed and sleep it off.

“It's like I could hear things going on, but it's like my eyes were shut … but I could just hear everything. I just didn’t feel with it at all,” Savannah said of being carried.

Harrison's friend, Aly, was also at the party. She said Savannah appeared to be aware of what was happening. “She was laughing, and she was fine.” Haley, another friend of Harrison's, said, “She was like, ‘No, I want to go back downstairs.’”

But Jessica said Savannah was barely coherent when she went upstairs.

“She was just like laid out on the bed with like her eyes closed,” Jessica said. “She wasn’t fully conscious, but she wasn’t fully unconscious at that point … she’s kind of really like a zombie.”

Jessica said she left Savannah in the upstairs bedroom to nap, but when she returned to check on her about 15 minutes later, she said the door was locked.

Jessica got another boy to try to open the door. When the door eventually opened, Jessica says she saw Harrison naked.

“I was like, ‘Oh my gosh. What just happened?’ Savannah, like half her body’s on the bed with like her arms back and then like half her body’s like draped off the bed,” Jessica said. “I started yelling at Cameron. I was like, ‘What are you doing? Like, she’s obviously not OK right now. Like, what are you -- like, why would you do that?”

Jessica continued, “He was like, ‘She wanted me to.’”

Savannah was completely out of it, Jessica said, and couldn’t even move. “She said, 'Just leave me here.' I was mad because she said that, so that’s when I left,” Jessica said.

Another 10 to 15 minutes later, Jessica said, she saw Savannah disheveled, wearing no bra and with her clothes on inside out and backward.

“She was slumped over the toilet throwing up, and she -- oh gosh -- she threw up so much. Like, it was at least 20 times that night. She just kept throwing up everywhere,” said Jessica.

Savannah says she has no recollection of any of these events.

The next day, Savannah learned from Jessica what she said happened.

“She said, you know, you and Cameron had sex, but you were really messed up. And I said, ‘You know, I don’t remember that,’” Savannah said.

Savannah made her friend promise not to mention it again and to pretend like it never happened. Initially, Savannah said, she didn’t feel like what happened with Harrison was rape.

“I was still kind of new, and he was who he was, so I knew that it’d be pointless to try and say something,” Savannah said of Harrison. “I just felt like he took advantage of me.”

And she sent him a Snapchat message saying just that. “U didn’t rape me. I mean u took advantage of me but I forgive you and I know you were drunk [sic].”

Soon rumors about what happened circulated throughout the school.

Savannah said she awkwardly ran into Harrison in the hallway, but they didn’t really speak to each other.

Later, during design class, Savannah, Taylor and their other friends discussed whether what happened to Savannah was rape.

“I was thinking like brutal, like holding, tied down, like gun to your head, tight, just very violent. That’s what I thought [rape] was,” Savannah said.

The girls told Savannah she was wrong, and they then searched for the definition of rape on Google in class. Unbeknownst to them, their teacher overheard and Savannah was sent to the guidance counselor.

“They were like, ‘You know, we’ve heard about this party Saturday night. You want to talk about it?’ And I kind of just broke down, said I felt like I had been, you know, taken advantage of,” Savannah recalled.

Savannah’s mother was called to the school, and then her father learned about what happened.

“Somebody can say, ‘She shouldn’t have got so drunk.’ Yeah, I get that. No, she shouldn’t have, OK?” her father, Joe, said. “I don’t care what she was wearing. I don’t care how much she drink. I don’t care if she was doing drugs. It doesn’t matter. Nobody has a right to take something that’s not theirs.”

Cameron, who heard the rumors, went to Savannah’s father on advice from a teacher to apologize and according to her father, told him the sex with Savannah was consensual.

“[He said] he only did our daughter for five minutes … only five minutes,” Joe said. “I told him to get the f--- off my property.”

Harrison has denied making that statement, according to Alicia McWhorter, a private investigator hired by Harrison’s mother.

A week after the party, Harrison was arrested for first-degree rape. He was released on bond, suspended from the football team and forced to take his classes online. He later pleaded not guilty to the charge on July 8, 2016.

Savannah stayed at school six more months before the family decided to sell their home and move out of Spanish Fort. She turned to blogging online about her battle and what she alleges was done to her.

“It helps. I feel strong that I can put that out there. I wanted to have a voice. I wanted people to see that I’m just a normal teenage girl who’s, you know, living just a teenage life,” Savannah said.

In April 2017, Cameron took a plea deal under the youthful offender status. The proceeding is allowed to be treated similarly to a juvenile proceeding, and nothing about the case is public. The case was settled in secret, with all the terms and conditions sealed.

Harrison and his family wanted to speak to “20/20” about the case on camera, but the terms of his plea agreement prohibit him from commenting further. Savannah’s interview with “20/20” occurred prior to the agreement.

Savannah forgives Harrison and says she went public with her story in hopes to inspire other young women who may have been sexually assaulted.

“I used to think that I was you know, weak, dramatic, too emotional, you know, couldn’t handle anything, and then going through this, I’ve realized how strong I really am and that I underestimated myself the whole time,” Savannah said.

Watch the full story on ABC News' "20/20" TONIGHT at 10 p.m. ET.