I feel your pain. Our male is 4 years old and is the exact same way, but it isn't just dogs he doesn't know, it is with one of our own, a male Golden Retriever. We have to keep them separated all the time. We have double gates so that they don't see each other at all but just like your situation, on the occasion that they fight, the bulldog starts it, but the Golden Retriever wins it. It is just an awful situation with an otherwise very sweet, fun dog. I think our situation is definitely caused by jealousy. The Golden has no care for any other cat or dog and had the Bulldog not started it, I think they would have been fine together. In fact they were for months! I know that we didn't get a handle on the situation early enough and I kick myself for that all the time. The only suggestion I can give you is to make sure you give your girl plenty of attention, but I would definitely keep her separated from visiting dogs for the safety of everyone (including the humans). In the last two fights we had between our dogs (in the last year or so), I was bitten once and my husband was bitten once, all while trying to grab collars to pull them apart. It is so dangerous.