Kids that age are looking for independence and learning the sense of control that it brings. I’d wager that because it was something she earned and brought home from her job, as opposed to the family’s food or something you bought for her, she sees it differently. While she might have been fine sharing food that you provided, this might be a deeper violation of her emerging sense of independence.

Not that I’m suggesting you make a big deal over her perceived offense or validate a sense of entitlement, but you might want to consider a simple apology of “sorry, I didn’t mean to overstep, I should have asked first”. It might go a long ways in this case, and engender a mutual respect that helps her to feel like more of an equal to the adults around her. Thats a very healthy affirmation at 17.

Might be a simple thing, but that’s the kind of stuff that makes young adults feel comfortable talking to (and listening to) their parents in their late teens and twenties.