'I think it is very important to be tolerant of others' dietary restrictions (speaking as someone who has some for* I 100% agree but suggesting everybody had to eat take away/ready meal was the inconsiderate part. It may well have been the man not the woman who suggested it though, not realising what a slight this appeared to be to the OP's cooking.'
It seems to be the man who has dealt, not very well, with all the communications. He may, however, have thought he was reducing the strain on the hosts by NOT requiring them to cook especially for them. He does seem to be very clueless about communications.
It is really the suggestion that they could just decide or not come on the day that would have put me off!
'If it is fussiness, uninvite them'.
THAT (and I realize it doesnt come from the OP) is the sort of attitude that can be hurtful to people with any sort of eating difficulties. There may be medical reasons which are not fully diagnosed (until my Crohns was diagnosed, which took several years, people often thought I was just a fussy eater); or which people are uncomfortable about discussing, like early pregnancy as may be the case here; and not everyone is comfortable about disclosing all their bowel and digestive issues to a near-stranger or indeed with receiving such disclosures.
In any case, even strong food aversions should be accepted, though the guest should be prepared to bring food along rather than demand that everyone should only eat what they can eat.
If it goes beyond 'fussiness' to an actual distrust of the host's hygiene in comparison to ready-meals, I would agree that this is rude.
One thing that I might suggest with regard to guests with food difficulties - though the current issue seems to have been resolved- is that perhaps invitations could be made for morning coffee or afternoon tea rather than a big meal. Then biscuits, sandwiches and/or cake could be made available, but without the same actual or perceived pressures for everyone to eat everything provided, or for the host to provide the perfect meal.