Report it and or take a different route when walking your dog. I would even make a video of the loose dogs for back up purposes. You own a bully breed, mix or not we have to take extra precautions with this breed. If or when something happens they take the blame whether it's their fault or not. Having some evidence like the video I mentioned might help. But at the same time knowing the circumstances, what have you done if anything, to prevent something from happening?

Which from what you just posted, it's not if something will happen but when. I guarantee you when it does, it won't feel like you're holding back a 45 lb dog. She won't just sit there and let you pick her up or hold her once she's in the zone with another dog coming at her. I don't care how much training she's had. Some of the dogs off leash may be friendly enough and want to meet and play with her but not all will be. Which is why she may be nervous at times.

There's a common saying about bully breeds "They may not start the fight, but they'll definitely finish it".

As her guardian it's your responsibility to make sure that doesn't happen. Which means keeping her out of and or preventing situations where it can happen, don't set her up to fail.

Whether she has never "bitten, knocked over, or attacked another dog" doesn't matter because it can happen. She has the genetics and the potential to do some serious damage in a matter of seconds,.. it only takes one time.