Why would a girl get so nasty?

I was bored and asking a question about a guy I know, who’s handsome and charismatic. Things just never worked out with him in the past; and I wondered if it was to do with my weight. Back when I was fat and unattractive. A younger woman turned nasty about it, rather than giving advice. Saying it’s pathetic for fat and plain girls to have feelings for such men. Then surprisingly, he read our comments, knew it was me and stood up for me. I’m just wondering what was behind the aggression of the younger woman? I am not a bitchy or dramatic type, so I’m not hurt, but I am genuinely confused. I also feel like I should know, as I’m Autistic and naive.

Why would a girl get so nasty?
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