How do you deal with a friend who has a crush on you?

That depends on how you feel about them. If you’re not interested in having a romantic relationship with them, gently let them know that you’re not ready to take that step with them. Say something like, “I’m flattered, and I really value our friendship, but I’m afraid I don’t have the same feelings about you.” If they keep pushing it and don’t respect your boundaries, you might need to stay away from them for a while or end the friendship. If you like them back, let them know! Accept if they ask you out on a date, or take the first move and ask them yourself.