This is the baby shower for second baby. I've chosen to do it slightly differently from last time
(www.mumsnet.com/Talk/pregnancy/3161664-Is-this-odd-for-a-baby-shower)
I thought my DM would be less of a pain in the arse this time round, but I'm already regretting involving her.
The other day she came out for a trip with DS and I. She tells me she's going to visit my brother at the Easter weekend.
So I said "Oh, you're not coming to the baby shower then?"
She looked massively confused and then horrified when she realised she'd forgotten when it was, then confirmed she'd swap the visit with my brother to a different weekend. Then I jokingly said that it would have been a bit awkward with just my mates and the nans. Again, she looks a bit horrified and admits she hasn't actually talked to them about it so they currently know nothing about it.
Then she asks if I've invited my SIL - meaning my brother's wife. (I have another SIL on DH's side) And I said no. I haven't invited either SIL because they both live hours away and I know that it's a huge inconvenience for both of them to make the journey from where they live. I also know that they won't be offended about not being invited because we've talked about this sort of stuff in the past.
Anyhoo.... DM then goes on for a few minutes about how nice it would be for SIL (brother's wife) to be asked, even if I know she won't come. Fine, I say, I'll think about it.
Later that evening DM sends me a guilt-trip text about inviting SIL to the baby shower. At this point I start to get annoyed because I can see my DM working up to some full-on manipulation. I ignore the text.
DM phones me at work today to ask when SIL's birthday is. She's forgotten. I tell her and she is annoyed I've remembered (and didn't tell HER 
) and have sent a card. Then she asks whether I've invited SIL to the baby shower yet. I said no. She tells me I should.
I, uncharacteristically, ask bluntly why she's pestering me about this.
She starts going on about she feels guilty and that she doesn't want SIL to feel excluded and how she wants her to feel part of the family and that I should invite her.
I pointed out that it sounds like she wants me to invite SIL because of her (DM's) feelings of guilt and that those feelings have nothing to do with me.
She says to me that she always invites her brother (to some really random stuff) and his wife, even if she already knows that he's busy playing football etc. (This seems bonkers to me) and that I should do the same for SIL because she (DM) doesn't want her (SIL) to feel left out of the plans we've made (she hasn't organised a thing, my best friends are kindly putting the event together for me)
This issue really doesn't have anything to do with SIL - I know she'll be cool about it all - this issue is entirely to do with DM. SIL and I have had frequent discussions about DM's master-level manipulation (she interferes in our relationship and plays us off against each other to get her own way) and have both agreed not to engage with it.
I'm now regretting involving my DM in the baby shower because she's already trying to manipulate the event into something she wants (it won't stop at the guest list - I can guarantee it) and acting like she's the organiser when she's just a guest. It seems such a small thing writing it down, but my DM really is the type of person where, if you give an inch, she'll take an entire marathon and claim all the credit and the sponsorship money (IYSWIM)
I'm now considering cancelling the whole thing and just going out with my mates.