She might not have meant anything by it. I've always been on the small side myself and have had many people get oddly confrontational about my weight, especially if they see me eat. I try to change the subject ASAP, usually mentioning that a lot of my work is physically demanding (which it is!). It's not a comfortable subject, as I'm very aware that other people have difficulty in this area and I don't want to rub it in.
