it really depends on other things like if she's looking at you. how is she looking at you? is she smiling with her eyes or did she look away when she saw you looking at her? it could mean so many things or perhaps you're reading too much into it. honestly, the safest thing to go by is if she's smiling at you. of she's smiling at you with her teeth showing then maybe. girls usually play with their hair like twirl a strand around their finger or tuck it behing their ears look up and then smile and then slowly turn away because they're either shy or blushing. like I said, it really depends on her other gestures.
It depends on how they flip their hair. If they do it to get hair out of their eyes/face. Or if they are staring/looking at you while doing it that could mean they are interested. People sometimes play in their hair when they are nervous, and when you like a guy it can make you nervous. I think you should pay attention to all the gestures along with the hair flipiping. When I like a guy I stare until I get his attention then I wink at him. I don't assume anyone is clairvoyant. I try to make it as clear as possible.
Looking at you holding your gaze for a sec or two then glancing down, smiling at you all teeth showing, a little sparkle in her eye, fliping her hair whilst looking at you then giving you a sweet half smile and glancing down again. If its hair flipping in this kind of situation then yeah