Are you a male or female yourself? I don't necessarily think that she should have to say anything back like "you're cute too." Even if she likes you.

If you're worried and hope everything's ok, tell her. If you want to know if she likes you, or want to express interest yourself, you could come out and ask.

She may be oblivious to you liking her, even with the "pretty" comment. And honestly I know its a "woman's world" now but its still also really not and if she herself is shy, you're going to have to express interest or something, if you're a guy.