If i am getting jumped? and if my mom opens the gate to let the dog out?

and my dog bites someone will i have to get rid of my dog. like get her out to sleep cause she attacked someone?

Well, I would say that if she had all her shots, and only bit someone becasue you were being jumped (she was defending you), they would do like a test or something to see if shes aggresive. BUT if she was defending you, then I guess no. Although I'm not sure and thats just what I would say. It might also matter in what state you live - I think... :)

Biting the person mugging you? Or bitting an innocent person?

If the dog bites criminal you "might" have no problem, that "could" be self-defense as long as the damage it's proportional to the danger; for example you can't allow the dog to kill the person if your life was not in danger. So the key is not to use more force than needed.

Now if the dog bites an innocent person then you can get in serious problems, s the victim dies then your mother can even get charged with manslaughter, criminal negligence (or even murder if the DA think it fits the facts). Not to mention a big lawsuit.

There is already a long list of people that have gone to jail in the US when their dogs bite and/or kill innocent people.

EDIT

But now being more realistic: How are the chances that you get "jumped" just in front of your house with your mom ready to unleash the dog to save you just on time???

I don't believe so as long as the dog was protecting you from serious bodily harm, but you never know what will happen with democrats in charge.