Answer:
I would say he should make friends with her. A good way to start a conversation with her would be to see something Caleb has in common with her (an example being that she is wearing a shirt from a video game, band, or movie he likes) He shouldn't force the compliments, as too many will make her uncomfortable, but as the conversation progresses he should be honest about what he thinks of her (as long as it isn't mean). Maybe she's really smart, so Caleb would say "Wow! You're pretty smart!" or something along those lines. Make it natural and make sure it isn't off topic. Just get to know her and learn about her. Be a good listener, but also make sure that you're a part of the conversation too. Learn what she likes and see if you like those things too so you can talk about it. Eventually, he can admit he likes her, but he shouldn't be angry at her if she doesn't feel the same way. He should be polite and treat her with respect, as should she.