I've been with my current girlfriend for over 3 years now, and in the beginning of our relationship it was exactly the same thing as you're describing.
The thing I did was taking her with me to meet my friends, male and female, so that she could realise there really isn't anything to fear. A couple months ago another girl even spent the night with me while my girlfriend was on holiday. I told my gf I was expecting a female friend to have a sleep-over and she was fine with it. I've known the sleepover girl since kindergarten and I wasn't willing to give up a friendship like that. Nevertheless, my girlfriend knows she can trust me and I haven't cheated once.
Your girlfriend just needs to realise that a good relationship is always based on trust, and with that trust comes a part of freedom. If not, the relationship is already doomed.
Hope this advise is of any use to you, I wish you and your girlfriend the best of luck.
The thing I did was taking her with me to meet my friends, male and female, so that she could realise there really isn't anything to fear. A couple months ago another girl even spent the night with me while my girlfriend was on holiday. I told my gf I was expecting a female friend to have a sleep-over and she was fine with it. I've known the sleepover girl since kindergarten and I wasn't willing to give up a friendship like that. Nevertheless, my girlfriend knows she can trust me and I haven't cheated once.
Your girlfriend just needs to realise that a good relationship is always based on trust, and with that trust comes a part of freedom. If not, the relationship is already doomed.
Hope this advise is of any use to you, I wish you and your girlfriend the best of luck.