First of all ... this is very important .... Never lie to someone you love. Actually, it's good practice to never lie at all. Liars make good cheaters and cheaters make good liars. You might not cheat but how can she ever trust you if you lie.
Now to the problem at hand. Don't back her into a corner and have her make a choice on demand. Even though it hurts, you are in a very good spot right now. Apologize to her if you truly mean it and hope she can see you are sincere. She needs this time for figure out if she could ever trust you again but if you push her, chances are it will be over. Should you be lucky enough to get a second chance ... just remember ... lying hurts the one you love and if you love her, you shouldn't want to hurt her.
Life is too short. Have a lot of fun and don't be afraid to fall in love.