I'm raging about this but really can't work out AIBU and/or what to do.
BIL (who is a very easy going character) had his birthday last week. DH and I sent him an amazon voucher in an amazon card - i.e a computer generated card.
It would have arrived the day after his birthday as I have to be honest and say that I forgot until too late to send it the day before.
DM has been at my DS and BIL's house at the weekend looking after DN. I spoke to her this morning to ask how she got on. All was fine, apart from the fact that she was looking on their mantle piece and was very disappointed not to see a card there from DH and me. I explained that I had sent one from Amazon. DM told me that this was really not acceptable. I should have sent a personally signed card from DH and me. Separately, I seemed to be relying on very unreliable people such as Amazon if the card hadn't turned up - although DM has never had a problem with them. The inference being that we hadn't actually sent anything.
For the avoidance of doubt, none of this will have come from BIL - I am quite certain of this. This is an issue that DM has. For example, we got married in September and I stayed with my parents the week before the wedding. DM spent a lot of time asking me if I had written my thank you letters for the presents that people had bought for us from the gift list - her and DF's friends would expect a thank you letter by now etc etc. Not very relaxing. I did sent all the letters pre-wedding and loads of DF's and DM's friends then told me at the reception that they couldn't believe that I was spending the days before the wedding writing thank you cards to them 
The long and short of today is I actually told DM that I didn't want to discuss this any further and put the phone down. I actually nearlly burst in to tears en route to work as it has upset me so much. DH and I have a very good relationship with BIL and I can't understand why DM is basically getting in the middle of this and causing a problem when none is there!
I'm not sure how to proceed now. DM and DF are coming to visit us with PIL's for my birthday in a few weeks and I actually just want to cancel the whole thing.
I know that DM will be absolutely convinced that she is the right here and I will have to apologise re the card and also for putting the phone down. I really don't want but I will if IABU. However, I really want to take a stand re this - I'm 33 FGS!