If it already hurts her too much, that should be a big confidence booster for you. If you make it bigger it is only going to hurt her more and I promise you this, the less sex you'll have and you will be more miserable. As crazy as it may sound, it could come to a point where she may seek men with a smaller package to please her.
Women want to enjoy sex unless they have serious emotional issues. If you plan on breaking up with her and being a playboy, you still have a great size anyway.
Imagine this reverse scenario, imagine having a true 10" x 7" cock and spending the rest of your life looking for that special someone that can handle and enjoy it and let's say after the long search and you find her, you find out she is an emotional wreck that makes your life miserable or better yet thinks you are still too small because she has issues, then what? Do more PE?
We all want bigger dicks to please our partners more. We think bigger dick means more climaxing for the partner. This is not entirely true. Most women have a hard time climaxing because of the pain it causes not to mention allot of women may already have pre-existing emotional issues and women climax off of fantasy unless men being visual.
Sure, many women that never had it, fantasize about having a big penis in them and once they get it and it hurts them, most of them never want it again. Just like us men have certain fantasies about certain things and once we experience them we sometimes realize it was not what we expected and wanted.