Sweetheart - first things first - look at @IncompleteSenten 's very complete & effective little sentence just above. Great, isn't it? You can do that.
Doesn;t matter if the rest of the group can hear or not - you only need your frenemy to hear you.
OK - next:
In any case I don’t want a massively awkward atmosphere all night, and if I am a joke it’s not going to stop them seeing me like that, because literally anything I do or say is funny because the fat ugly one is doing / saying it.
Will you stop being so horrible to yourself?
If you feel like this around this group, there's a reason for it.
They are maybe a bunch of bitches, or your frenemy is & makes you feel uncomfortable or like an 'odd one out'.
Sadly, some people never grow up past the playground in terms of how they treat other people. Perhaps she is one of them.
How well are you supported at home?
Now you are a mum, have you maybe found that your friendship group has diminished?
Do you have the freedom & funds to join a hobby or interest group - with & without your DC? Say, an evening 'off' once a week while DH does the parenting & you do something just for you?
This is clearly playing on your mind - it would on mine a little bit too, tbh, but I am long in the tooth & no longer take pass-agg nonsense from shitstirrers so ...
Annoying as it is, it's maybe less about "handling the repetitive remarks" than "wondering if this woman is actually my friend".
Does that sound accurate?
If so - you don't owe her anything, & you are 'allowed' to distance yourself from her.
Or you could decide "today I am meeting frenemy for coffee & I am going to be IMPERVIOUS" ... but I might start small by raising my eyebrows incredulously/pityingly when she trots out her usual schtick ...
And in the meantime - a new interest for you, mum. You are more than a woman raising a child, & you might find it very refreshing to carve out some regular Me Time to do some independent adulting in. With the bonus that you will gradually attract new, & maybe more emotionally intelligent, friends.
