Paint, which is basically QH + color. And yes, it is a breed, but that's essentially what the breed is just to give you some more info, if you have a lot of QHs that makes sense.
It's possible there's something else in there. I could go with pure Paint, Paint x, QH x... but definitely a large portion of one of those. She is a little heavier then average, but not enough to make me convinced there's anything else in there. She's also obese which throws off the eye.
It's tricky cause some horses mimic purebreds... I could see a Gypsy x QH (lighter build) ending up like this for example. And while QHs can be more easy keepers it's possible that there's something else that's even more of an easy keeper in there. Or she's just overfed lol
I've known plenty of purebred stock horses with good bone like she has.