There is a third tzad: that you owe her nothing .
she dropped the meat into your pot the meat she dropped is gone, batul it doesnt exist anymore .
why would you have to pay her back with other meat? If she dropped it on the floor would you have to pay her back?
In fact if you had 59 pounds in your pot, she might have to pay you for ruining your meat !
true you gain a bit from her clumsiness but so what?