Jesus is contrasting what Mary is doing with what Martha is doing. It may be helpful to make this explicit. Alternate translation: "the only thing that is really necessary is to listen to my teaching" or "listening to my teaching is more necessary than preparing a meal" (See: [[rc://en/ta/man/translate/figs-explicit]])
Possible meanings are 1) "and I will not take this opportunity away from her" or 2) "and she will not lose what she has gained as she was listening to me" (See: [[rc://en/ta/man/translate/figs-activepassive]])