If the story is like he says it is, then the girl knows exactly why he cut contact.
Well, you don't actually know that.
He said basically nothing to her.
She might not have a clue it was because she's fat.
And I don't want to be the guy who starts questioning how we can trust what hillkill has said (although I guess I am now), but we've not seen how fat this girl was, or how fat she appeared in the photos she sent. I mean, for all we know, he overreacted to her not being skinny.
It's not like she turned out to be a 40 year old man.