If you and your gf feel strongly that her trying out someone big would be a good learning experience for both of you, then you should explore the possibility further but proceed cautiously. All the negative reactions here are from people who couldn't imagine it working out, but for some of us (including my wife and me), this kind of experimentation is a worthwhile and positive experience. You have to be ready to accept that it might cause a breakup--you might lose her. But if you stay together, and you express all your feelings to each other about it and learn from it together, then you will have a much stronger bond than the average couple. My wife and I have been together for almost 30 years. (We experimented with stuff like this during the first few years, mostly.)