Her life before her involvement with X-Factor has not been revealed, all we know is that she had been a reporter for a long time and that she was once married.
She was sent to cover a story about X-Factor, that at the time were posing as mutant hunters but were actually protecting them, suddenly Vera Cantor appeared and was about to be interviewed by her but were interrupted by Beast; it was Trish that gave the name of X-Terminators to the teams other facet. She continued in her story about X-Factor and was constantly questioning their ways, she covered the story on Freedom Force trying to capture Rusty Collins and Skids, she also received inside information revealing that Warren Worthington III AKA Angel, a public mutant was the one funding all of X-Factor affairs, a supposedly mutant hating group. She released the story.
Warren was hospitalized after the attack of the marauders and got his wings damaged, Trish managed to get into his room and began interrogating him on why did he was giving money to X-Factor, she also told him that a court order was sent that forced him to amputate his wings, this information had been kept from him.
Warren was believed dead after an apparent suicide when his wings got amputated, she attended to the reading of his will and told the rest of the members of X-Factor that Cameron Hodge was the one behind everything, Warren's wings amputation and the fact that he was leaving all his money to him, at that moment they were attacked by The Right and she was badly injured but rescued by the elegant Beast.
She was hospitalized. One day she was roaming at the hospital when she encountered Beast, whom at the time was affected by Apocalypse and every time he used his strength he got dumber and dumber, they shared an intimate conversation until interrupted by Iceman who explained Hank's situation to her. When she got out, she released the story on Hank's McCoy loss of intelligence, this made Beast really sad and angry at her.
She was shortly captured by Warren that at the time was going by the Death persona, he wanted information on Candy Southern that supposedly was the one that leaked information about him, Beast saw this and tried to stop Warren but was quickly knocked down by him, Warren left, Trish was surprised to see this act of heroism even after she released the story on him. They grew a little closer.
When Beast recovered his intellect and his blue fur thanks to Infectia, Trish had a real hard time accepting this new Hank, not only about the beastly appearance, but also on the intellect, the vocabulary, the jokes; but she managed to realize that the sweet guy she knew all along was still there, after she defended him from some mutant hating humans they shared their first kiss. They soon formed a relationship and she got closer to the other members of X-Factor, they even double dated with Scott and Jean. She became almost like the exclusive reporter on mutant affairs , she covered some big events like the X-Tinction Agenda on Genosha.
Her next big step on her career was releasing the story on the Legacy Virus and it's lethal effects, she also revealed that it not only affected mutants as it was believed but a human infected case was reported ( Moira MacTaggert), Beast confronted her, he was disappointing on her, since the release not only helped humans to have a cause for hating mutants but also the proper studies for the case has not been made. This was their first big fight, he told him that thanks to her pursuit for ratings she already caused that a bunch of humans beat a mutant to death, she responded by saying that it wasn't her fault, she was doing her job and if the X-Men had done theirs that kid would still be alive.
Hank was captured and replaced by Dark Beast (An evil Hank McCoy of another timeline), when he escaped he looked for her, he told her that he had a lot of time to think and realized that one of the most important things on his life was her, so they got together again. During this time they enjoyed for stability.
Her next big professional move was to get an exclusive interview with presidential candidate Graydon Creed who was running his campaign heavily on mutant hate, she confronted him but his political charisma got the best of her.
Journey Into Space
One day she was out on a date with Beast when they along with other X-Men were captured by the Shi'ar, they needed the help of the X-Men to put an end to the threat of the Phalanx, surprisingly enough she was excited by the whole adventure in space thing rather than frightened or angry. During this time on space she and Beast got to spent time together and grew closer, when they defeated the Phalanx and were returning to earth, an alien vessel got them off course and they landed in a strange planet, in this place mutant powers were suppressed so she got a chance to share a moment with Beast in his human furless state, things started to get strange when Nanny appeared saying she was going to take care of Magneto ( Joseph), they realized that they actually fell on earth and were in the hidden base of Magneto on the Savage Land, after they defeated Magneto and Gambit was put on trial they escaped the place.
When they returned to the mansion she was confronted by Wolverine, who blamed her on all the problems mutants were having and the apparent death of Professor X, due to her releasing the news of the legacy virus, after that she returned to her job as a reporter.
She followed the events of Magneto's attack on earth, he disrupted the electromagnetic field on the whole planet until the united nations agreed to gave him Genosha for him to rule, following that she also covered the events of Eve of Destruction. When Beast went through his secondary mutation and changed his appearance, Trish couldn't get used to be around him and they broke up, after some time she was sent to the mansion to cover an exclusive with Jean Grey, she got caught in a fight with Cassandra Nova and was rescued by Beast, she tried to apologize to him, but he stopped her and told her it didn't matter that he was gay anyways (a lie, a joke), she released the story and didn't made sure if it was true.
Hank later admits that he said he was gay in order to gain revenge on Trish for her harsh breakup.
She reported the events of M-Day, after that she haven't been seen much.