YANBU - this could have been me 18 months ago.
SIL and MIL were both invited to my hen night - neither came - not an issue but what hurt the most was neither of them in 6 times of seeing them between the invite and the hen do did they say anything direct to me. I saw MIL the week after and I mentioned hen night and she didn't even ask if I had had a nice time.
SIL had been asked to make our wedding cake at DH request (my sister also makes cakes) found out 6 weeks prior to the wedding that what we had asked for, which had been very simple to suit her confidence in cake making, we weren't getting. Sizes were wrong so not enough cake, no decoration was going to be done - very simple decoration planned. In the end my DH had to drive (2hrs each way) to collect what she had done, we had to make another tier to make sure we had enough, and then drive it to my sister (2 hrs in opposite direction) for her to finish it off for us.
SIL was also a bridesmaid - somthing I felt obliged to ask - later to regret it. Dress shopping was done in 1 day with my other two bridesmaids - she was exceptionally rude to my sister within an hour of meeting her. Sulked when I picked the dress they all said they liked but wasn't her top favourite. Looking back from this point on she was a cow about the whole thing.
When the cake issue arose - there was a big fall out with lots of hideous things said to me from her - really bitchy comments etc.
In the end my DH asked her if she actually wanted to be a bridesmaid and if she could promise to not be miserable around me on the morning of getting ready etc - and she was honest and said she couldn't as she didn't feel comfortable as she knew no one. Wanted MIL there which I put my foot down about as I didn't want her there as my mum is no longer with us so didn't want a 'reminder'.
2 weeks prior to my wedding I ended up having a stand up row in a restaurant with SIL and MIL who still to this day can not understand why being let down and having all sorts of accusations thrown at me which were completely unfounded caused any upset.
She didn't speak to me at all on the day didn't even wish me congratulations.
Moral of the story - if you can suck it up, don't say anything. 18 months down the line there is still a tension there, I hate spending time alone with them as I am always on edge - not helped by distance and not seeing them often. Am dreading their behaviour when baby arrives in the next two months.
Someone further up said something about SIL worrying about brother being taken away - this sums up my situation 100% - all the accusations stem around them not being able to tell him what to do all the time as he has to consider me as well now - and they don't like it.
Venting is good - and there is no way I would say you are a Brideszilla - I hate the term because as soon as anyone states what they would like on their day apparently you become one. You can't plan a wedding by committee!! Yes some people take things a bit far but someone has to make the final call sometimes!
Sorry turned into an essay!!