It sounds like your friend is sending you a very unclear signal. She could just be being friendly and playful and joking around. Maybe she is just a very “touchy-feely” kind of person. She might be interested in something more than friendship and be doing those things as a way of expressing her interest in you, but might be too scared to tell you. If these actions are bothering you, you need to tell your friend that she is making you uncomfortable. It can be as casual as saying, “Hey, it kind of weirds me out when you grab my ass in public.” There should be no reason for you to feel uneasy around your friend, so if you need her to change this behaviour, you should tell her. If it does turn out that she likes you as more than a friend, you may need to be ready to tell her that you do not feel that way about her (if you don’t) or re-examine your feelings for her (if you do or might). At any rate, your first step should be to tell your friend if what she does bothers you and see what happens. If she’s a good friend, she’ll listen to how you feel about what she does to you. Good luck!