"Switches crushes easily?" Come on man, get real. First of all... if she even gets "crushes" at all, she's not worth having around. I mean... this is High School right, who in the hell gets crushes anymore? Secondly... being interested in a lot of people at one time is something that should happen. (in my humble opinion) It is for this reason that I always tell my younger friends to either casually date (I'll get into that later) or date girls for a short period of time (90 days or so). Options, options are important, and experiencing a lot of different girls (not a slut like sense) is also a good thing. Now back to your question... merely treat her like every other girl. Do not worry about her wandering eyes or mind... she's going to do it regardless. As long as she's interested in you, whatever else she may be glacing at is irrelevant.
Sucker Love Is.....