My dog started disliking certain breed.?

My 1 year old Bull Terrier mix has suddenly became a bit too aggressive when she plays with Labs and Golden Retrievers. She lets a Doberman pup pull her around and abuse her, there are a couple of Mastiffs at the park that she loves playing with a bit rough, and most other dogs she ignores. But Labs and Goldens, it's like she turns into a rabid wolf with them sometimes. She starts playing with them and suddenly just snaps and starts snarling, showing teeth and jumping on them. We've had to pull her off 3 dogs at the park already. No one got hurt of course and the owners said it was ok. I however don't think it was ok and I'm afraid she might hurt them one day. Anyone know why she only bullies those two breeds?