I told a girl she's pretty and now she's not talking to me (10 POINTS BEST ANSWER)?

So she is shy. She probably likes but does not know how to respond to you're compliments. She maybe very inexperienced with guys and maybe she's analyzing you and her feelings. Don't give up, be persistent if you really want her. Show her that you can be sweet and be patient with her shyness. Try and talk to her again