Maybe she needs to go to a doc. Nothing should hurt her- fingering, sex, or anything even if she is a virgin. Her sexual status has nothing to do with the mechanics of it all, and it should not hurt her.
I will say this again- if something hurts her, it is wrong!!! STOP!!! If you can't even get your fingers in there without pain, don't even think about a penis. That's just mean. When did people stop caring about the feelings of their vaginas?? I love mine and would never let anyone hurt it
Are you absolutely sure she is well lubricated? Are you using lubricant? Does she orgasm before you even try to enter her? Try starting with oral and getting her good and ready (see if you can get her to orgasm with oral before entering) and DON'T put anything in there until she is ready and it won't hurt her.
If that isn't working, she needs to see a doctor. Something is wrong.