Just as a legal quibble, because I'm that kind of person :-), I'd say she might not know about legal ownership, or might not care about making a precise distinction among slaves HE owned, slaves SHE owned, or slaves owned by her family ... if all of them were part of the same household. No reason why it would particularly matter to any of them, unless a sale or a will were immediately planned.
Who owns "my" van? The loan is in my name, the title is in my husband's name, it was purchased in a community property state ... doesn't matter, really, unless there's a death, divorce, sale, or default.
In Falwell's biography of Jackson, he states that the couple owned between 6 and 9 slaves. At least two were owned by Jackson before the marriage. Three slaves, a female and her two teenage children, were brought into the marriage by Mary Anna Morrison. A sixth, a female child, was purchased by Jackson after the marriage as a gift to his bride with the expectations of making a ladies maid out of her. Two or three other slaves were sold shortly after the marriage and the proceeds were used to purchase a house and property for the couple. Whether these slaves were also brought into the marriage by Anna Jackson or whether Jackson himself owned them prior to the marriage is not clear.