Everyone has insecurities, maybe about their body, their looks, or even their capabilities. Even if the person has done a lot of self-work to deal with those negative feelings about themselves, it might still hurt if other people point out those qualities.
This is what a woman faced from her sister-in-law, who would always fat-shame her. The in-law kept putting her down for her weight, even at her wedding dress trial. Eventually, the poster’s fiancé found out about his sister’s behavior and uninvited her from their wedding.
More info: Reddit