Mueller is the last known remaining American hostage in Syria, but on Friday, ISIS claimed she was killed.
Three days later, the US State Department says they have no information supporting those claims.
Mueller was taken hostage a year and half ago.
Only a small group of people knew, but her name became public on Friday when ISIS claimed she died.
Mueller dedicated herself to helping suffering people.
As a student at Northern Arizona University, she became a national student leader with the Save Darfur coalition.
Erik Leaver says she quickly became a national student leader, a testament to her compassion and service.
"It could have been a lot of us, but she was the one who was special and so determined to make a difference and was willing to go under the group and provide medical assistance to those who need it most," said Leaver, with United to End Genocide.
Mueller's family says she was leaving a hospital in Syria in 2013 when the terrorist group ISIS took her hostage.
Many reporters learned of her circumstance, but kept it quiet for her safety.
One of those people, a student journalist at NAU, connected the dots when the white house chief of staff inadvertently dropped Mueller's first name during a television interview last month.
"It did spread around campus, not a lot, no more than 20 people knew, that's still a lot of mouths to keep quiet," said Kevin Morrow, an NAU student journalist.
Then Friday, ISIS published Mueller's name and claimed she died in a Jordanian airstrike.
The US government has no proof that she is dead and her parents said in a statement that they have hope she is alive.
"Everything I've known about her, and I've done a lot of research on her and she's been the focus of my life for the last couple of weeks, and from everything I've learned, she is a fantastic human being and probably one of the best students our university has put out," said Morrow.
"We hope she is still alive and that we can find out what really what's happening. where she is and hopefully we are in a position some day to bring her home," said Leaver.
Mueller's parents have asked her captor's to contact them privately.