There is a very simple rule when wondering if a lady is interested - if she is interested, she will let you know.
So look if the signs are there - not just if you would like them to be, but if she really is giving you signals.
Any doubt, and take it she is being friendly. Misreading signals caused embarassment all around, and it;s easily done - usually by men who are experts at seeing what they would like to see, not what is actually going on.
So take it a step at a time, watch her eyes, if she holds eye contact and smiles, she is interested.
Good luck.