This teen lost her little sister in the Uvalde massacre. Now she's channeling anger into activism.

In some ways, 17-year-old high school senior Jazmin Cazares is like so many other teenagers. She can get bored easily, loves to sleep in and dotes on her attention-seeking dog.

But since June, she’s been spending 30 to 40 hours a week pushing for gun reform in her red home state.

Uvalde:365 is a continuing ABC News series reported from Uvalde and focused on the Texas community and how it forges on in the shadow of tragedy.

Cazares' 9-year-old sister, Jackie, and 10-year-old cousin, Annabell Rodriguez, were two of the 19 children shot and killed with an AR-15-style rifle at Robb Elementary School in Uvalde, Texas. Two teachers were also slain in the May 24 massacre.

Like the Parkland high schoolers who came before her, Cazares is channeling her anger and heartbreak into advocacy.

"I didn't really plan on activism," Cazares told ABC News from her Uvalde bedroom, which is filled with her original artwork and an extensive collection of crystals.

"I would've waited a little longer, honestly," to get involved in advocacy following the May 24 massacre, she said. But at a June rally, a March for Our Lives official encouraged her to take the mic. Cazares was apprehensive, but once she started speaking, the nerves dissipated.

She told the crowd about the morning of the shooting: she usually bumped into her baby sister in the bathroom before school, but on May 24, the 17-year-old woke up late. She told the supporters she felt guilty for not remembering the last thing she ever said to her Jackie the day before.

Jackie loved gymnastics and Starbucks and dreamed of going to Paris when she graduated, her sister says. The sisters planned to save up and go on a trip.

"She was getting to that age where she wanted to be grown up, so she was taking my clothes," Cazares said. "With that age gap especially, there’s things that we couldn’t really connect on...In hindsight, [that] makes me feel really guilty, makes my parents feel really guilty, that we could have done more together."

Cazares, who keeps a photo of her little sister on her bedroom mirror, said she's finding activism helpful for her grieving process.

For about one week after the shooting, she said her family "didn’t really do anything, and it was really hard, because we're left alone with our thoughts, stuck at home. It was a lot harder whenever you can’t focus on anything else but what happened."

Cazares testified before Texas lawmakers in Austin in June, pleading with them to pass gun safety legislation. She returned to Austin in August to demand that Gov. Greg Abbott call a special session to raise the minimum age to 21 to buy an assault weapon.

The 17-year-old hopes to see a ban on assault weapons, but she added, "Being realistic in Texas, I think raising the age to 21 is the absolute bare minimum."

Abbott's press secretary, Renae Eze, said in a statement to ABC News that "federal courts have made clear that the Second Amendment prohibits raising the age to buy a semiautomatic rifle from 18 to 21."

Eze cited a ruling by the California federal court of appeals in May that said the state's law raising the age to purchase semiautomatic rifles was unconstitutional. A month later, she noted, the U.S. Supreme Court struck down a New York gun law and a Texas federal court, following the Supreme Court standard, struck down a state law in August that restricted gun rights for adults under 21.

The press secretary said the governor "continues to work on solutions focused on the root of the problem: mental health." She added, "Governor Abbott and First Lady Abbott join all Texans in mourning every single innocent life lost that tragic day, and we pray for the families."

Cazares said another school shooting is "inevitable -- it’s gonna happen again no matter what."

"And as much as we’re trying to prevent this from happening … without the help of our government, we’re not really gonna get anywhere," she said.

"We’re not trying to take away your guns," she explained. "If you are a responsible gun owner, you would support bare minimum things."

Cazares has joined forces with March for Our Lives, a nationwide group founded by student survivors of the 2018 high school shooting in Parkland, Florida, that killed 17 students and teachers.

Parkland survivor David Hogg, an outspoken March for Our Lives leader, turned his Twitter account with 1.2 million followers over to Cazares to share her story. Cazares never expected to be fighting alongside the well-known Parkland activist she'd seen so many times on TV.

Her parents, Gloria Hernandez Cazares and Javier Cazares, are taking action, too, traveling with their daughter and advocating for change on social media. Javier Cazares is now running for a county commissioner seat, the family told ABC News.

The 17-year-old says she is still getting used to being a "public figure."

She said she feels like it's easy to forget "we are real people. I grieve, I cry, I have panic attacks."

Jazmin Cazares said she and other siblings of victims are also battling survivors' guilt.

"Everybody keeps saying, 'Oh, it would never happen here.' It happened everywhere else, of course it can happen here. No one just expected it to be the elementary kids," she said. "We thought if this was ever to happen, it would be us high schoolers."

"People don’t understand the genuine guilt we feel for even waking up in the morning, let alone having fun," she said.

Devoting up to 40 hours a week to advocacy is "rough and it’s extremely exhausting," Jazmin Cazares said. But she said, "If it would have been the other way around, I think my sister would have done the same thing. She would be in the spotlight the way I am...that’s really what keeps me going."

ABC News' Kat Caulderwood and Ismael Estrada contributed to this report.