Vanessa Guillen's sister reacts to military sexual assault reforms

Mayra Guillén, the sister of slain Army Spc. Vanessa Guillén, said the newly passed reforms to the way the military investigates sexual assault honor her sister "in the best way possible."

The House passed the 2022 National Defense Authorization Act on Dec. 7, and the Senate passed it Dec. 15. The bill makes sexual harassment a crime under the Uniform Code of Military Justice and removes military commanders from "decisions related to the prosecution of covered crimes," including sexual assault.

It now heads to President Joe Biden's desk for his signature.

"This has been a very hard time for us," Guillén told ABC News’ Juju Chang. "These almost two years of fighting for justice and fighting for what's right has been very exhausting."

She added, "There's a trauma to all of this, but thank God that we're here today."

Guillén was 20 years old when she disappeared from Fort Hood in April 2020. Her remains were found along the Leon River in late June that year. According to the U.S. Attorney's Office of the Western District of Texas, Guillén was killed by a fellow soldier in the arms room of the Killeen, Texas, military base.

An Army investigation released in April determined that she had been sexually harassed by a supervisor and the leaders in her unit did not take appropriate action after she stepped forward. Twenty-one soldiers were reprimanded or disciplined as a result of their handling of the case.

Investigators found that the incidents of harassment were not related to Guillén's murder and were not carried out by the soldier who is alleged to have killed her.

The family’s attorney, Natalie Khawam, said the new legislation will give soldiers protections they never had before, possibly saving lives.

"Commanders are there to fight a war and teach our soldiers how to win a war; they're not there to be the judge and jury of whether sexual harassment or sexual assault existed," she said. "That's an unfair situation for both the victim and the person who has to make that decision without the training that they need."

Guillén told ABC News her family visited the offices of several senators to encourage them to pass the bill and highlighted Sens. Kirsten Gillibrand and Mazie Hirono for advocating for this issue.

"This is something very personal, and I feel like our voices must be heard in order to make changes possible," she said.

Guillén said her family plans to keep advocating for reform in the way that the military handles sexual assault and harassment.

"My family is day by day trying to have a normal life again after this traumatic past year and a half," she said. "We're slowly but surely trying to be the family that we were before. And even though we have a great absence among us, I know that she's very proud to see what we were capable of doing in her honor."

ABC News' Luis Martinez contributed to this report.