Should I tell my best friend I love her?

You should definitely tell her you at least like her, don't creep her out by saying you "love" her right off. It sounds like she says she likes those guys because she WANTS you to say something to her about you two. Just be upfront and be like "I don't want this to make things weird between us, but I like you and have had feelings for you for a long time and I can't stand the thought of you being with someone else because I feel like they don't deserve you."