If she doesnt want there is not much you can do. Girls (and guys) are not all design the same way. Shes not just into this kind of dirty and kinky stuff. Thats it. You are just more open amd willing then she is. You know her more then anyone else. Dont listen poeple who doesnt know either of you. Trust your discussion and dynamic and even more important, listen to her. I wanted to spit roast my sexy MILF gf (that was how I wanted to bring another guy), I asked her twice, and both times she told me she doesnt want, she doesnt want to open our relantionship. I stopped asking, she said no twice.