I gave my elderly, disabled mother a very energetic pit bull
Why would you give her a pit bull.
I heard it's the most loyal dog
You may be right about pit bulls' loyalty, but it is wrong to give your mother such an energetic pet. You could be putting her in danger by giving her a dog that she can't control.
Good, I wanted her to have a hard time and it's better that she gets that dog than those boring cats.
It is wrong for you to put your mother into this situation, and the fact that you take pleasure in it is highly worrisome. I can understand if you want her to get more outdoor exercise, but you should not have given her a dog that could be too strong for her. I suggest taking the dog back, and getting her a small, manageable dog that she can walk.