Hi,
It all depends. Everyone is different. It may take 1 month, 2 months, 5 months etc. By that time you will know if she loves you by the way she acts toward you. Actions speak louder than words. If you tell her you love her and she does not tell you she loves you too and her actions don't show she cares, then maybe she does not love you.
After a few months, she probably will tell you or if not, ask her again.
Good luck to you.