Since home birth may not be an option, what about going to a different OB for a second opinion? Since you are still 31 weeks I don't think it's too late if you started looking now. Maybe you could find one who is willing to help you have a vaginal birth. I don't really understand why your OB would suggest an elective c-section already and yet not be willing to use forceps if it really came to that? Seems like very odd reasoning to me.
Why would she not strip your membranes if you are positive for GBS? I was positive last time and they never stripped mine.
I hope you can work something out, she sounds very unreasonable and unbendable!