I adore my MIL and FIL and we get on really well. Having said that, we also got married last year and money really is the route of so many issues with family...
My parents gave £5K (plus paid for my dress etc) and his parents gave the same amount, plus the dads/grooms suits and half our honeymoon, so both gave about the same and we covered the rest ourselves.
We only had 6 months to plan it and even less time to pay for it all (as payment is usually 6 weeks in advance) so it really was important to know ASAP how much we were getting to establish what we needed to contribute personally and if we had to get a loan etc (we didn’t). I didn’t mind how much anyone gave, it was just helpful to know ASAP to then establish what we would need to find ourselves. I would not have been offended if no one gave us anything! I think you DIL is unreasonable and slightly stupid to not confirm with you the amount before perhaps committing to something…
My DH had in his mind (as they could easily afford to!) that his parents would cover “the rest” of the costs, above what my parents contribution would cover. This issue stemmed from his dad saying that they would do that over a curry night together, to then have his mum saying to us both a month later that they’d ONLY get wedding cars and suits (but only both dads and the grooms, not the three groomsmen….and we didn’t have cars as it was all on one site) then it was changed to a lump sum and the suits…. Then it went back to just the suits…..in the end I offered to speak with ILs just to get a figure or “stuff” they were comfortable with, with no pressure from me for anything if that was how they felt. (They were uncomfortable paying anything for their “sons” wedding as they felt this fell on the brides family, but my dad when speaking to him pointed out his son had got the same as his daughters did for his wedding and my DH subtly passed this on which seemed to unlock things! I genuinely didn’t mind getting nothing, but my DH was quite hurt when they could afford to help and my dad had less and would give more if he could!) We were getting >4 months to the wedding with no real idea of what we had to find money for! In the end DH spoke with them and they kindly offered £5K plus suits and honeymoon. DH chose to say to them we’d accept what they were comfortable giving and may have made a comment FROM HIMSELF he’d hoped for more (as they have more) but that wasn’t from me and they know that.
Once we’d confirmed all this, his mum found our photographers wedding pamphlet in our kitchen and because it’s SO well priced, it had the package prices on the back of it - which was £2.4K for ALL day videography and photography. Having got so many quotes, this was a steal as many want that just for photos!! She then kept making comments about how she “didn’t see photography as a worthwhile investment” or having any value and it being a waste of money. My DH then admitted he saw her reading it and this was why. DH said they’d not want “their money” spent on certain things (like photography) but my parents had already given us their money and we’d paid most of the venue off and the big things (like florist and photographer) between that and our own money already….so I wasn’t going to lie and give them credit for paying for such a huge thing as the venue/food or any of the big stuff when their money largely went on the final touches which I really loved and they made the day special, but my MIL didn’t see value in. (We also booked a Photo Booth for £200 and she kept saying it was “for the kids” before the wedding….And my husband got our new name in big wooden letters for £150 for the entire day and she hated that too 😂
(I’ve been financially independent since aged 19 and I’m now a commercial lawyer on a good salary who is also financially very sensible and so while I don’t mind advice, I won’t be TOLD what to spend my money on for my own (very reasonably priced!) wedding…. My DH is also on a good salary, but has had a lot of “gifts” from them in his adult years and has advised these tend to come with strings.)
the point of all of the above is perhaps have a think of anything you may have said to your DS he will have repeated back? Men repeat EVERYTHING to their wives - I just know people are human and don’t hold a grudge, many do!
I think offering to meet for lunch is a lovely idea. You may never know exactly why she clearly feels less comfortable but as I said, it could be something your son repeated that you meant nothing by and she took offence to about the wedding or other OR it could be something similar to my story above where small comments are made without thinking. I know I’m quite laid back and forgiving, but many aren’t.