She's always been a little snippy at most female dogs, but some in my neighborhood she's friends with. Recently at the dog park, it's hard to tell exactly what sex they are when they come up to her, but it's been every dog she's had a problem with (besides the rat terrier).
Last summer (before my sister's dog came into the picture) at the dog park she was very playful and I never had any worry she'd start something with another dog.
When I walk both dogs together, she's interested in the other dog, but as soon as she smells for a minute, then she immediately starts snarling and going for their throat. When I walked her alone, for the most part she'd be friendly enough. I do wonder too if the rat terrier's barking is making her feel protective.