"I pointed out there were a lot of dates we could all do and she came back and said she wasn't sure I'd feel comfortable at the event as she was also inviting a lot of her clients, I phoned her to ask what this was supposed to mean.
"(My) sister is a personal trainer, I am overweight (size 16). Cut a long story short she started by saying everyone going was really slim and cared about their weight (my anger rose to about 5/10 here), then she proceeded to suggest it looked bad on her as a personal trainer if she had a 'fat' sister (anger soared to 10/10 at this point!) …"
The woman said she hung up the phone on her sister, which she had never done before.
"I am fuming!!!! What do I say to her?" she asked.
Fellow mumsnet users were quick to reply in supporting the clearly upset woman.
"I can't actually articulate a response at this point as I am: O. I get why you are at a 10 though," one person said.
"Oh my god, that's horrendous. In your position I would be writing on group chat that I/you feel very hurt that not only has she deliberately excluded you from an event (i.e. basically uninvited you) but that her reason for doing so is that you are not a size 8, gym-fanatic."
"Alternatively invite all of the family BUT her to some other event!" another advised.
A third disagreed, saying that she should say nothing to her sister.
"She needs to apologise. Vile attitude. Hopefully one of your family will deal with her nastiness."
Others described her sister as being "horrible" and "rude".
The post has since been deleted.