Hendrix and Olivia Benson were in the police academy together, but two years later Hendrix decided "her time was better spent shrinking heads". Hendrix eventually became a psychiatrist and worked at Bellevue Hospital.
Benson and Hendrix disagreed several times during "Weak". At one point Olivia said their schizophrenic victim, Miranda Cole, who was missing, should have been kept in the hospital. Hendrix argued that they couldn't force her, that she was allowed to check herself out unless a court compelled her to stay. Olivia said that's the problem with the mental health profession - that they medicate people long enough so they can be cut loose and that then nobody monitors them. "They go off their meds and the next thing you know they either become the victim of a crime or they commit one. Either way, we have to clean up your mess." Hendrix then asked Olivia if her solution was "locking them up", to which Olivia replied, "If it keeps them safe, yes". Hendrix then said that she left the job because she got sick of locking them up, that she'd rather treat the criminals and help the victims. Olivia finally asked her if she thought Miranda was being helped now on the streets.
Throughout "Weak", Stabler sided with Hendrix several times instead of backing his partner's play, which clearly bothered Olivia, and later on, when he asked his partner what her problem was with Rebecca, once again stating she was a cop, Olivia said Rebecca "didn't think that being a cop was good enough, so she quit". Stabler responded by accusing Benson of having an inferiority complex, to which she replied, "You know, I get that you're on the rebound and all but if you could keep it out of work that'd be great".
Hendrix called the SVU squad when a nine-year-old girl named Holly Purcell, who survived a car accident with her parents was believed to have been a victim of sexual abuse. Benson and Stabler originally arrived on the scene, and Casey Novak gives them court-ordered permission to carry out the exam. Hendrix still needs the presence of the police to document the progress of the examination of Holly, and though she prefers not to have any strange men in the room, Holly seems to take comfort in the presence of Detective Stabler. When the test results confirm her abuse, she works with the detectives as well as her parents to try to find the girl's abuser. Originally Holly was too terrified to reveal him. Using her talent and interest in art, Hendrix tried to use Holly's artwork as a means of uncovering the man who molested her, which she originally believed was Mark Dobbins a friend of the Purcell family. Eventual evidence of Dobbins' innocence and further examination of one of her drawings, revealed that the Holly was molested by a boy named Kevin Wilcox the captain of the school lacrosse team. (SVU: "Contagious")
Hendrix once again helped the SVU squad on the case of a couple of teenage twins, Logan and Lindsay Stanton, who were involved in a crime. They were born in Bellevue, so Rebecca pulled their medical files and told A.D.A. Casey Novak she might want to subpoena them, stating that even though she couldn't say the twins were at risk, "there are several red flags". Novak insisted she needed to know specifics or she'd be going on a fishing expedition, so Hendrix agreed to tell her what was "not in them". She said she had never come across anything like this, that entire chunks had been redacted. Novak then asked her to order the complete files, but Hendrix said she couldn't do that because their therapist pulled her off their case as soon as they were admitted, and that she'd already overstepped her bounds by reviewing the medical records. Novak then said that if there was a case she'd have tainted it, but Hendrix said she had to find out why they were seeing a sex therapist.
Later, Hendrix ended up telling Lindsay what the records said, that she was actually born a boy, and the twins' psychiatrist, Dr. Blair, said he'd report her conduct to the medical review board. He threatened her saying "You're finished". Hendrix's last scene in the episode showed her in her office, packing her things. She told Stabler and Benson it seemed she'd "lost her privileges" at the hospital, and that that'd give her time to prepare her for the hearing over her license. When Stabler told her she did the right thing, she then told him, "for a cop". (SVU: "Identity")
Dr. Hendrix's next appearance was in the Season 7 episode "Ripped", which saw Stabler working on a case involving the son of a cop named Pete Breslin, who used to be his partner. During a scene in the courtroom's bathroom, where Breslin was beating up his son, Stabler broke them up, but ended up losing control and beating Breslin pretty bad. He then went to see Hendrix in what appeared to be her home, and opened up about the abuse he suffered as a child at the hands of his father.
Hendrix's last appearance to date was in the Season 8 episode "Philadelphia", in which Captain Cragen, worried Stabler and Benson might be too close, submitted them to a psychological evaluation, which was conducted by Hendrix. She interviewed the partners separately and then told Cragen "Detectives Benson and Stabler have a degree of mutual reliance, an emotional dependence, that compromises their effectiveness as police officers. They're too close". When Cragen asked her if she recommended he split them up she replied, "If you want to lose your two best detectives".