I don't personally see any bully breed in her, either.
With puppies it hard to tell. I could believe she's mixed with a Border Collie, but personally don't see (scotch/lassie) Collie in her. I could also believe she's mixed with shepherd. Her independence might just be her age, 4 months is often around the time dogs realize that humans aren't always the center of everything interesting.
Even if she were mixed with a bully breed (which, again, I personally don't think she is, given the pic), it doesn't guarantee bad habits or behavioral problems and it doesn't make her dangerous or anything like that. Train her like you (hopefully) would any other dog, exercise her, and teach her what is and isn't OK to do and she'll be fine. The issues that make pits/bully breeds a challenge don't crop up in all of them and really aren't unmanageable issues, they just are things that can make them not 100% perfect for everyone like some advocates seem to think. High prey drive, high energy, and issues with other dogs aren't uncommon in bully breeds, but neither are they super uncommon in many other breeds, including Border Collies and some Shepherds (although in their case the prey drive is usually channeled more as herding drive, and the issues with other dogs may be rooted in different things).