Reporter: Daisy coleman doesn't remember much about the night that changed her life. She remembers sneaking out of her house to meet a group of older boys, that brimming shot glass. But what came... See More
Reporter: Daisy coleman doesn't remember much about the night that changed her life. She remembers sneaking out of her house to meet a group of older boys, that brimming shot glass. But what came after, including, she says, losing her virginity with senior matt barnett, that is a blank. A blood-alcohol test of daisy, taken seven hours after the encounter, showed her still nearly twice the legal limit. But her mother is convinced she knows what happened. There's no way that it could have been consensual with her being that drunk. Reporter: At the the hospital a doctor's report cited -- "alleged or suspected sexual assault." At first, authorities seemed to agree. We were able to pretty quickly put together names of people that we needed to talk to, and subsequently some folks were detained and ultimately charges were filed. Reporter: Barnett was charged with sexual assault, a felony, and endangering the welfare of a child, a misdemeanor, for leaving daisy on her lawn in 21-degree weather. That's not all. There was a video taken. We were told that immediately after they did that, that they deleted it, and when that phone was forensically examined, there was nothing on the phone. I had a couple good friends tell me about it. They had seen it firsthand, and they instantly text me and told me. Reporter: Charlie coleman is daisy's oldest brother. Was the girl in that video saying anything? Was she saying no? They just said that it started with my sister and him kissing with their pants off. Reporter: Whatever happened the close-knit farming community of maryville was now reeling. For melinda, a terrifying realization that the boys who melinda thought could have been her daughter's protectors may have been her tormentors. I ted them. I thought they were good kids. They were at my house all the time. And you know, I really thought these boys not only would not hurt my daughter, I thought they would've protected my daughter if she did something stupid like this and snuck out and drank. Reporter: Some of your friends even turned on you guys and your brothers. Uh-huh. I had a buddy inform me that there was a twitter chain going on about a couple of guys waiting for me out in the parking lot after school. Reporter: Melinda says she watched her daughter's life unravel. Daisy was suspended from the cheerleading team after admitting to drinking and was bullied at school. People would generally just yell stuff. Like, they would yell, "liar," or the "s" word, or they would call me the "w" word. She would sometimes, if i took her to walmart or the grocery store, start having an anxiety attack, and I'd have to take her home. Reporter: Daisy's friend paige, the 13-year-old with her that night, says her personality also changed after the incident. I don't really go out anymore. I just don't like being around a lot of people. And I don't do very much anymore. Reporter: Paige's 15-year-old assailant's case was handled in juvenile court, and those records are sealed. But soon after the incident, melinda says she heard speculation that the charges against barnett, the grandson of a former missouri state representative, would be dropped. I thought with all the evidence that we had that there was no way that was even a possibility. Reporter: And sure enough that felony charge was dismissed. I was just in disbelief. I tried for weeks to contact the prosecuting attorney and find out what had happened. What's going on, why'd you drop the charges? I was really upset. I felt like I lost a lot of faith in the justice system, especially in maryville. Reporter: Prosecutor robert rice said there wasn't enough evidence. And with that, melinda says the town turned on her daughter and sided with the popular high school football player. The stuff on facebook and twitter was just unbelievable, so horrible. Things like, "why don't you slit your wrists." I saw the bathroom was closed. So I knocked on the door. And there was no answer. So I tried, like, opening the door, and it was locked. And I just had this, like, weird feeling coming over me. Like, "oh no, not this. Not this. Please don't let it be what it looks like." So I kicked in the door, and she was just, like, laying there unconscious. So -- Reporter: Melinda had seen enough. Shved her family out of maryville, 40 miles away, but the family's troubles followed them. Eight months after leaving town, another blow, the house they were trying to sell burned down. An insurance company called it an electrical fire. And all the while daisy's depression deepened. I began self-harming, and i was very suicidal. And I really started to hate myself and who I was, and I felt like I was just an ugly person. I got to the point that I had her with me every single minute. It was almost like having an infant again. She was in such a dark place. Reporter: Daisy was down, but wouldn't be silenced. She went on a national media campaign. I felt really weak, worn down. Thank you, both of you, i know it's difficult. I think they need to pay at least some punishment, so he can learn. Reporter: She ignited a firestorm back home. The local prosecutor bowed to public pressure. To take a fresh look at the case. After a ten-week investigation, yesterday, the final word. Today, mr. Barnett pled guilty to second-degree. It's a conviction, it will replain on his record. And it will never go away. Reporter: That was for leaving dazy on her lawn in the cold. No evidence or sexual assault charge. There was insufficient evidence to go forward on a sexual assault. Prosecutors can only bring charges if they can prove the elements of that charge. So, in this case, prosecutors felt they had insufficient evidence to prove the charge of sexual assault. Reporter: As for political favoritism? Barnett's lawyers said there never was any. Mr. Barnett truly regrets to the actions to which he pled guilty. Reporter: How did that make you feel if. Of course, I'm sad and disappointed. But it's better than nothing. Reporter: But for daisy things may never be resolved. As recently as last monday, she tried to take her own life again, and tonight, she is recovering in a psychiatric hopsital. Despite her struggles, her message for other young girls like her remains the same. I really wish more girls would tell their story because i have heard multiple stories. And they've come to me and they've told me their story, and they've told me that they're not brave enough to go through and tell someone about it. And I really wish they would, because they deserve justice
This transcript has been automatically generated and may not be 100% accurate.