when the band gets together, for rehearsal or whatever, and before anybody has got drunk, ask them to listen and explain the problem as you see it, not in an accusatory way, but just as a statement of the ground rules you expect.
this way the internal culture of the band can change, and you will then have the implied support of the band as a group in all situations, without having to perform surgery on a friend's digital extremities.
i don't know how you are perceived, or perceive yourself, but i would say something like "guys, how would you expect to have to behave if there was a woman in the band? .... well, there is one - me!"