One of my Sim households is the 3rd generation child of my current game's founding family who is attending her 2nd-to-last term of University. She has the Single and Lovin' It lifestyle but has developed a couple of romantic interests and, as her time at Uni comes to a close, I'm planning on her picking someone to settle down with.
Here are the main contenders:
Celeste Frost. The local bartender at the Britechester student commons. Currently also already married.
Mary-Therese Uchiyama, a fellow student who is majoring in Villainy.
Brighe has the traits Outgoing, Self-Assured, and Perky, is majoring in communications, and will be pursuing the Social Media - Public Relations career.
I'm currently leaning toward Celeste, even though that will involve breaking up a marriage. Both Celeste and Mary-Therese are born-in-game sims that I haven't edited at all in CAS and, to be completely shallow, I like Celeste's look. She has genes I'd like to add to my current family.

I do also like Mary-Therese's look, just not as much, and I don't know how I feel about her apparent plans to pursue villainy. Though that would make it interesting, as I've never gone that direction with a played Sim before. Pursuing her also would mean not needing to break up someone's marriage.
Comments
The Winters family Tree --- My Mods
However I have to admit Mary-Therise's character looks very interesting. Proper vs master in villainy sounds very fun.
....I didn't even know that could happen. I've always been the one to initiate that interaction normally.
The Winters family Tree --- My Mods
I agree, that's the main reason Mary-Therise is in the running. And why I'm so torn. Brighe has a twin sister (not identical), maybe I'll introduce whichever one she doesn't pick to her....
The Winters family Tree --- My Mods
She's not just a bartender, she's a mutant.
I honestly have no idea how the game decides which sims will 'get-on' with which other sims, but the chemistry between them looks so real when they are interacting.
And these are from the follow up date where Celeste called and asked Brighe out the following night:
The Winters family Tree --- My Mods
Worth mentioning that "Frost" is her (current) married name though. Her maiden name is "Kyle"; she's the daughter of Vanessa Jeong and a randomly generated Sim named Sergio Kyle.
The Winters family Tree --- My Mods
http://fanphoria.blogspot.com/
https://twitter.com/FanPhoria
Alternately, I tend to treat villainy as one option for sims who attend law school, first making them do their degree that is linked to one of the law careers to represent their bachelor studies and then adding villainy as law school. But then again, I play with aging off, so I can afford wasting time this way.
She's also winning in the votes.
Approaching 1 day left for a final decision and that's the direction I'm most strongly leaning.
In another twist to the story, Brighe visited Celeste in her home and learned that she has a child! The child, Diana, is not from Celeste's current marriage. Brighe also met Ice, Celeste's husband, and though he's a decent enough guy, he hates children, and it showed during Brighe's visit.
This is a good story arc along the lines of what @FanPhoria suggested, wherein Brighe not only falls in love with Celeste but also sees pursuing her as a way to 'rescue' Diana from a father figure who doesn't love her and doesn't even want her around.
Ice is also a University student, so it looks like he's pursuing an education while making Celeste work a lot of hours to better support them. Celeste deserves an education too.
Brighe meeting Diana while Celeste watches the interaction:
At this point, I think I'm going to add Celeste to my played households rotation and play through the romance from both sides, as well as playthrough Celeste breaking it off with Ice and moving out with her child. This will give some time to play through single motherhood with Celeste while she and Brighe develop things, and also let me take her through University to pursue a degree program. A single mom, raising a kid on a Bartender's salary while also trying to improve herself with an education will be at least semi-interesting to play out for a while, until she marries into the Winters family (who are filthy rich).
The Winters family Tree --- My Mods
Hmm maybe it's cause of the Story Progression Update. Do you have any mods though?
The Winters family Tree --- My Mods
If Brighe can convince Celeste to break up her marriage, what's stopping someone else from convincing Celeste to do the same to Brighe? Celeste is so gone right there.
As for Mary-Therise, no also. Opposites attract is great for a summer romance, but for a relationship? No way. Mary-Therise's traits alone scream drama queen. Hard pass.
Brighe can do so much better, and deserves better. Unless...if you want heartbreak for Brighe, then go after Celeste. If you want misery for her then pursue Mary-Therise's drama.
Under The Tartosan Sun
Schemes and Dreams
The idea that "once a cheater, always a cheater" makes the presumption that all relationships are equal and that the person with whom the cheater is involved has no bearing on the outcomes. That doesn't align with Brighe's self-assured trait. The idea that one should 'stick with' an unhappy marriage rather than move on and try to find happiness doesn't align with her "perky" trait.
The Winters family Tree --- My Mods
I guess it really does come down to Celeste or someone else. Mary-Therise is non-starter with her traits.
Under The Tartosan Sun
Schemes and Dreams
I also then moved Celeste and her child out and into a small apartment in Evergreen Harbor and will put her into my played rotation. I will play her and her child in the rotation until she and Brighe move in together and/or get married. I haven't actually played her yet though (I rotate households on Fridays in my game, it is Thursday right now).
Thank you everyone for helping us come to this decision.
It's also worth mentioning that Celeste's Ex re-married another Sim immidiately the night after Celeste broke it off...so he apparently had a side-dish. (Or, more accurately, I had MCCC set way too high in terms of the chance of YA sims getting married and have reduced it to account for the frequency with which I actually turn on unplayed household aging).
The Winters family Tree --- My Mods
Culling deleted Celeste's ex-husband's household, along with his new wife and their new baby. Just gone, poof. Because Celeste is now a played sim and had a full friendship bar with him (as well as a very negative romantic bar) and he lives in a house, I got the in-game alert saying he was moving 'off the grid' when he was culled.
...that's one way to deal with a break up, I guess...
The Winters family Tree --- My Mods