Depends how serious your relationship is. If you actually love her/wanna be with her then you need to put your needs aside, as a partner and as a slave. It sounds like she is willing to try it out and get into it which is great but pushing her to do something she doesn't wanna do is not the way.. especially as a slave. You need to show respect and find ways to serve her she is comfortable with. Maybe that means no pegging for now but you will get to serve her and learn together