Should I contact her?

Try in person first because then you can gauge her reaction. She may ignore your text otherwise. Good luck, just treat her right (vice versa)!

She seemed OK but was a bit cold that day. I tried to get her attention 2 times, 1st time she didn't see me or probably ignored. Second time also, I was near her , she heard my voice but wouldn't look up until I was waving to her then she saw me . Did not wave. Just smiled.

Oh, I see. If she's the one being aloof, then maybe she's not worth it. If it's too much pressure to confront her in person (which I completely understand), then perhaps give her a final chance by text and ask how she's been.

Yeah but u think sje got upset that I didn't text

If someone asked for your number and then didn't contact you, you'd be a bit upset too! Why didn't you text this girl?

Approach her in person as you've let her down; text is too impersonal in this case.

Told her will text but did not so after that I feel she was a bit cold but still smiled :/

Well, like others have said, just give it a shot. Try to talk to her, and if that fails, text her.
If all fails, leave her be.

Thanks

Tho did I make a mistake :/

Oh? what mistake?