It's hard to tell really. Looks like she might be an Old English bulldog or possibly have some Boxer in her. You would have to ask the folks you got her from, they should really know for sure if she's mixed breed or not. Either way, welcome to EBN to you both and to her authentic looking poodle chair she's got there in the fourth photo. Almost looks like a real poodle. LOL.
Bella is a cutie for sure. Long tail is a giveaway for not being pure bred BDog but as cute as she is, we’ll love her as much as any here. Looking forward to watching her grow up.