I really like the play between Carter and Lex, but I think you were really smart to give them some distance you can play in by introducing Nikki. I probably like Carter more, because he seems like such a good sport and a lot of fun. Alex can be really hard on him, but I get that that's her personality. She doesn't seem like a girl who lets her feelings be known through words or overt actions. She buys him breakfast because she cares about him. She gives Nikki a ride, because she cares. You've done a great job giving depth to Alex for sure, and it will be interesting to see how she grows throughout the book!