She's never been the preferred child. As far as she can remember, it's always been Tori. Tori has always been the daughter her parents doted on and were proud of. Somehow, Tori managed to land the spots of both daddy's little girl and mommy's go-to gal for "girl stuff." She doubts her parents even liked her very much the few months when it was just her before her mom accidentally got knocked up again. Hell, they act like it was some sort of miracle. Really, it was just a glorified mistake.
She doesn't hate Tori. She hates how perfect she is, but even she isn't cold enough to care about her own sister. Trina's wanted to be a star ever since she knew what it meant. She can't sing or act, but she's been working on those skills all her life. It's not even about the money like everyone assumes it is. Trina has a passion for the stage, for performing, and it's the only thing that keeps her sane sometimes. Tori, however, she never wanted it until she found out she was good at it. Cat and Jade may be better singers than her, but even Trina can't deny that she's a natural performer. Lucky bitch.
Really, she's the bitch of the two sisters. Tori is sweet and genuinely caring, not to mention loved by everyone and everything she came across. She's the kind of girl who's always going to be known for being one of the rare celebrities that doesn't lose her mind. Trina, on the other hand, is never going to admit to herself that she's going to make it. Maybe she'll always be living with her parents, (when it's Tori who they'll never want to leave) but she'll never stop performing to anyone who will pay $5 for an awful show. She's too much of a bitch for her few audience members to feel bad for her.
At first, she pretty much despises that Robbie Shapiro kid. He's awkward, annoying, and icky. When they kiss for a play audition, there are no sparks or any indicators of chemistry. Slowly, things start to change. She finds herself missing his obsession with her. She tells herself that she just misses the attention. After all, attention is all she's ever wanted. But Robbie's also sweet and a good guy who listens and she realizes he's everything she never knew she wanted.
She hangs out with Tori's friends more often to see him. She can deal with the antics of the emo chick and she finds she actually kind of likes the bipolar one. Robbie kind of has a thing for every girl he sees, so she does make some progress with him before she realizes that he likes every girl he meets, but he loves Tori. He freaking worships her just like her parents do. Eventually, Tori decides that she loves Robbie, too. Trina knows it's just because a relationship with him is easy and safe. He'll adore Tori forever and he'll never break her heart.
So it goes on like that. Tori takes one more thing that Trina wants. It's not intentional. It's not Tori's fault that she's perfect. Life's never been fair to Trina Vega, and she doesn't know why. She's not that bad of a person. Still, if there's one thing she's been given over her sister, it's that she doesn't take things lying down. She'll never be the kind of girl that gives up on herself. She loves her sister, but she's not going to sit around and watch her parents and the man that should be her boyfriend drool over Tori.
Tori doesn't love Robbie. Everyone thinks she does, but Trina knows her sister and knows that Tori is in love with Andre, but is too scared to act on. She does one year of junior college in the area, waiting for him to graduate. Then, she runs away with him. He's talented and going places and willing to treat her right. They don't even leave a note. Trina and Andre skip town together and they get jobs and his is actually in performing. Trina works at a restaurant and she doesn't really hate it. She has a nice life with a nice man. Sure her boyfriend is in love with her sister, but she's in love with her sister's boyfriend. It isn't a relationship built on love, it's one built on creating a life where they're no longer second place.
For once in her life, she has something that her sister wants but doesn't have. She has Andre, and she's going to have him until the day Tori's brave enough to leave Robbie for him. He has Trina, and he's not planning on leaving her until that day. That's the deal. They're not going to wait around while Tori messes around. They're going to build a life and chase their dreams. It's not really what they want, but it's enough of it to keep them going.
She ends up marrying Andre and she has no regrets.