Well, of course, any opinion given here is only a guess. To me, she looks like a mixed breed from a long line of mixed breeds and the only way to know for sure is the DNA test. And that can be wrong, too, I have heard they are not at all reliable.
One way to guess mixes is to think about what is very commonly seen in your area. So, if there are a lot of pit bulls where you live, there is probably some of that in there - if they are not seen in your area, then less likely. Black mouth curs are not commonly seen in certain areas. (Which doesn't mean she doesn't have that in her if she came from that part of the country where they are common).
One way to guess mixes is to think about what is very commonly seen in your area. So, if there are a lot of pit bulls where you live, there is probably some of that in there - if they are not seen in your area, then less likely. Black mouth curs are not commonly seen in certain areas. (Which doesn't mean she doesn't have that in her if she came from that part of the country where they are common).