Whats going on with this chick?

So I play varsity basketball right. This guy was a senior (im 16) and he graduated. His sister is the same age as me and plays ball to (both of us are white, she is actually no bad looking). Anyway haha. During our season last year (the last few practices) she had never said a word to me (she isn't shy) and she always said hey CJ whats up. Right well I thought it was nothing. So she apparently had a bf and she broke up with him and she was crying. Then she was talking to this other guy and she was crying in the corner. So we have our sports banquet and she was like staring at me the whole time. Not smiling. Just staring. She also found out we played basketball together when we were like 4 or 5. And she called me her kindergarted buddy...So! Is she a slut (moving from guy to guy with emotional problems), Or is she just being friendly (wouldn't explain the staring) or is she in to me? So anything I can do (always see her at the gym) to like idk see if she likes me besides the usual whats up? Hahahaha