First let me say on behalf of bully owners, thank you! Thank you for opening your heart and home to a controversial breed. Its so heart warming to hear that you are aware of your dog's issues and are working and loving it regardless
OOh muzzling could defintly make her aggressive. Did it sound like the shelter was warning you about her specifc behavior or just the natural behavior of the breed?
One of the reasons she may not have displayed aggression around the other dogs is because you mentioned you encountered them on walks....versus in a situation where either dog could potentially try to protect the area as its own.That makes a big difference.
I have a pit bull, she has NEVER shown aggression towards any other dog but as a responsible dog owner I have to keep in mind that the potential is there. The potential is there with ANY dog but obviously the damge our dogs might cause is considerably greater then that of most other breeds. However this is what I do with my girl. I dont take her to off leash parks or beaches. Even if she is leashed, the otehr dogs who run up to her freely may make her feel defensless and even maybe lash out.
Thankfully there are 5 dogs in my close family, meaning my sisters and aunts, I chose to socialize Rory with. I chose this because she had to get used to them sooner or later, obviously she needs her puppy play time, and it teaches her canine body language so she knows when other dogs wanna play or are telling ehr to back off. I didnt want toerhe dogs to be such a taboo thing or she might become fearful, agressive, or who knows what else. I'm not saying we dont walk where ever we want for fear of her meeting other dogs, she meets plenty of otehr dogs on the walking trail, at the pet store and controleld places like that. But the dogs she gets to play with off leash with abandon are limited to these 5.
If the other dog is nice I say meet at a neutral place like a gated park or school that has been let out for the summer. Somewhere neutral. Pay close attention to their body language. Allow a certain amount of talk between the two, they will establish alpha on their own. They might do a bit of growling, thats ok. Try not to interfere unless you have to. If either dog acts up DONT praise the dog, they will think its ok to act that way, be firm but not mean.
Lastly: pitties, dobies, rotts, and staffies play hard! When Rory plays with my sister's pit bull it sounds like murder! Some calmer breeds are like "what the heck is wrong with you", ha ha! You'll be able to tell the difference. Goodluck adn keep us posted!