yes sometimes you can be a "kissing friend" with one of your pals. this means that the kiss really has no meaning, and that it just feels good. be careful with that situation if you are an emotional little B*cth. You can get carried away with that and then get your heart broken.
as far as foot massages, i would not use your crush on me to get free foot massages. i am not saying that is what she is doing, but it is possible. if you like doing it because you are a good pal, then have no worries. just don't let yourself be manipulated, okay?
However, some people would see a foot massage as an intimate act, others just as something nice to do for a friend. My husband used to have his army buddies pay him for foot massages, yes he is pretty good. but that doesn't mean he wanted to kiss them. or at least i hope not. hahahaha. J/K
Bottom line: if you enjoy giving the foot rub, and you enjoy kissing, keep it it up. sounds like you have a good deal going there. but, if this situation is messing with your head; then it is time to set some boundaries and protect your emotions. and don't be afraid to ask this girl straight up about how she feels. good luck.