I'd be peeved! BM is more precious than gold, especially to a hungry baby. It's not like it is that easy to supplement something else for it. I think it was really inconsiderate of them. If it was an accident, fair enough but if they purposefully used your milk for coffee, I would be so cranky.

Why should it reflect badly on you? You did nothing wrong but knowingly taking someone else's BM and putting it in coffee is the same as stealing to me.

Can you tell I have strong opinions about this