I sent her a text which read: "Hi [her name], I just wanted to say that I think you're very pretty!"

Her: "Okay thx, that was very random."

She hasn't talked to me very much since then and takes longer to reply to messages. I occasionally catch her looking at me and she always almost immediately diverts her attention to her phone.

Did I come off as creepy or too strong? If not is there something else I did wrong?