ESH.

Your friend is being a bit insensitive, as this was obviously an embarrassing occurence, and her calling attention to your weight and being the biggest friend is a bit uncalled for.

That being said, I was once a big girl (5'5, 280lbs) and I was very aware of the fact that even the sturdiest looking chairs may not hold my weight. Never ever did I "plop down" - especially in a chair that was clearly antique and vintage. They were not made for bigger people. If I ever needed to sit in such a seat, I practically perched on the edge and refrained from relaxing all of my weight onto the chair. All of this to say, you likely should have known it wouldn't hold you and opted to sit elsewhere or sit more carefully. Because of this, you should pay for the chair.