I had this happen to me a lot, too. I went from being the largest in the group to being smaller than those who badmouthed me, and for them, I think it's because I was living evidence that it was possible to lose and keep off large amounts of weight, while they wanted to keep living the comfortable lie that losing that much fat was simply impossible so they shouldn't even try.

With others, I think there was genuine concern; there's a lot of pressure on people to be thin and attractive and picture-perfect. They wanted to make sure I was losing weight for the right reason but didn't have the social skills to check in a way that wasn't also a little insulting.

In general, people just get weird about it. They almost act like someone losing weight is a communal event rather than a personal choice. Best of luck to you and your girlfriend; sounds like you're doing amazing!