I'm going to roast her badly about her weight
Why are you going to roast her about her weight.
She looks like a fucking whale and I'm sick of it
Well you shouldn't do that to people. It sounds like this is being done in revenge to begin with.
Fuck you, don't you understand she is fat. I hate her body so I'm going to roast her out.
I believe that she is heavy, but it is wrong to make someone feels bad about their looks.  If you do not like them, I would stay away from them.