I actually have a theory that I can’t prove, that perhaps a few of the pieces we attribute to Wolfgang were actually hers. Here’s why I think that…

We know they corresponded regularly after she got married and that she continued to compose and send her brother her work, and he wrote back praising her. I have a suspicion that he might have given some of her pieces to be performed, telling patrons they were his. Not to take credit, but so her music would at least be heard.

Again it’s not something I can prove, more like a headcanon thing.