Lexi doesn't always find happiness if you make one specific choice.Congrats on the play through. Dont worry about Lexi on your Cece run, she still finds happiness, so go for it. Drifty does very well at making sure that most of the girls have a happy ending option even when you don't choose them, you don't have to feel bad because you chose someone else.
As for the real Lexi, if there was one, she'd be mine, so back off.
Going for Cece or Steph and making the right choices allow for the "best" ending for the group with the least number of single people.