You would benefit from looking up indicators of interest (IOI's).
Some of which are:
1. she holds eye contact,
2. she scratches her hand, touches her hair
3. you notice her body language is friendly and open as well as leaning or pointing body parts towards you.
4. if she is or has been touching you.
5. if she is cooperative with requests.
6. if she gives you compliments.
7. if she is willing to become isolated with you, (leave with you or even leave friends to be with you)
Hope some of these help you out. If you look up indicators of interest you may find a few more besides these main ones.
Best of luck