I suspect also that a lot of mothers of women getting married now may well have got married 20-30-40 years ago themselves and as such had much more parental/mother involvement as it was more done then (and likewise, they would have experienced even more themselves).
As such, particularly if the dm had to have lots of people that she didn't want at her ceremony or do things differently from the way that she would have wanted, she may well have spent years planning 'her' wedding - ie her dd's (yours!) wedding as she comes from an era when it was the bride's mum that did lots of the decision making.
Of course, times have moved on and these days brides are pesky and want to sort out their own weddings, not have the weddings that their mums want them to have
. It's good for the brides obviously - but sad for those mums that have fallen into the middle changeover years where they're young enough for their mum's to have taken over their own weddings but old enough that their dd's do their own weddings, meaning that they never get to have the input that they had been dreaming of for years...
Doesn't mean that you should give in to her demands though!
Maybe worth keeping in mind as one explanation of her behaviour - I know it's a huge generalisation, and it won't be true for many many people, but having been experienced it with my mum and seen friends experience it with their mothers over the years, it definitely seems to happen to a fair few!
Dsis got married first so she got the brunt of it in my case - I found that talking to dmum about her memories of her own wedding, as well as her expectations and hopes for mine was useful - both to remind her that she didn't like being dictated to for her own wedding (thus why would I want to be dictated to for mine, when she has successfully raised an independent critical thinking dd!) and to find something that she liked that I also liked and would have gone for anyway to let her think that she was getting some input...
And of course there's the fact that they still think of you as their little dd (and still will do, even when you are both claiming your pensions!)... suspect that's always going to be hard one to break!