I have finished the Lexi path today and the game just doesn't feel right when you are with another girl, even though I feel a bit more positive about Cece's future in that ending.
So for the game to work the best, you have to pick Cece on your first playthrough. And for you to do so, the game has to nudge you a bit. Make you attached to her.
For you, it was the kiss. For me, it was the mystery - I wanted to know "why". And for someone else, it might be her "finding Nemo".
Unrelated questions:
1) Does the score in the hospital affect anything? I got 13/15 the first time and 8/15 the other time...
2) Is there a solo Holly path?