I just finished my 4th playthrough of this today, and no matter how many times I say I'm going after a new girl (Judy, Mi-do, etc) I just can't.
I don't put myself in a place to think how many guys Carli has been with. I've done all my walk-throughs with her and never ever touched anyone else. I just can't bring myself to do it. I've done 2 play-throughs in CoBD and have chosen 100% Katie both times, no matter what I say I'm going to do before I start the game. #2 was supposed to be a focus on Chandra or Ellen. Didn't even pay them any mind.
I don't go into the game thinking about Carli's past. I just learned today that she has a 3some scene with Stella. So not interested. I like to think that once the MC "has" her, that she's as pure as she can get. I don't care about her past, all I wanted is for the MC to have her future.