How to tell...?

[Peter L]

No, no no. Don't base it off a blush man. Chances are it is in your head.

Talk to her, she might like you but will say no in your face and never speak to you if you ask to early...but do not ask too late. And when I say this I mean it. talk to her. Flirt with her, get her number, socialise. Then when you're sure you can:

Be a man and kiss, then ask her out.
Ask her out and kiss later.