First time poster and long thread but please hang in there!
For background my DM is a very very difficult person to put it nicely. My DP’s split when I was 4, the typical mother stopped father seeing child because she was bitter scenario took place and my father got to see me EOW on the basis he paid CSA and extra in cash on a certain date (if he didn’t , he didn’t see me, court order or not, this was years ago when police wouldn’t of done anything) . Anyway, she is a good mum in many ways, but has major demons/problems and was very manipulative, controlling and emotionally and sometimes physically violent towards me. For example , when I was little she would tell me if I slept at my dads she would be in the house alone and he would sneak out when I was asleep and kill her. Therefore I was terrified to sleep at my dads, I wouldn’t tell anybody why as I was so scared and she ‘won’ because everyone thought I just didn’t want to spend time with my dad (I was a huge daddy’s girl and her behaviour still affects me to this day- anxiety etc)
She cut herself off from all 4 of her sisters, her father (basically all her dads side), most of her friends , all my godparents, hates her neighbours, my grandmas neighbours, anyone really! Could start an argument with a cardboard box! 
I went to live with my DF when I was 10 through a court order where I was old enough to be part of the decision making, we then didn’t have much contact at all for years and then whatever contact we had was difficult/traumatic etc until I got back in contact properly when my grandma and grandad died 6 weeks apart 2 years ago. Since then a lot has happened and she has been great in many many ways, supportive of my DP (older and dad didn’t approve 
) helped me with all sorts and I am obviously grateful.
Anyway this was years ago and I thought she’d changed a lot, however now I know this isn’t true!
I am 28 weeks pregnant with my first baby, However, I didn’t tell my DM I was pregnant until I was 10 weeks (me and DP wanted to make sure all was actually okay first at early scan, just my way of thinking) and she was annoyed rather than happy when we told her that she had been informed after my cousin (who is basically like my sister and was told at 3 weeks as I needed to tell someone!). She straight away said ‘well I’ll be annoyed if Im not in the room when you give birth’ and I said oh you can be if you like. 1. Because I was on cloud 9 announcing the baby and was feeling very positive about mine and my DM’s relationship 2. I didn’t want any arguments if I said no (which there would be)
Since being pregnant for the last few months, my hormones and thoughts have changed a lot and she has acted strangely on many occasions throughout my pregnancy. A few examples, she rang me in hysterics (knowing I’d only just been released from hospital hours earlier due to horrendous pains in stomach thought I was miscarrying etc) about some colleague at work and starting saying ‘I’ve definatley got baby brain my hormones are everywhere’. when my grandma paid for our nursery furniture my DM wanted it delivered and assembled to her house (???) however on being corrected she didn’t argue just sulked, she is also point blank refusing to be called grandma, nana, nan or any of the appropriate wording for a bloody grandmother, she has come up with some ridiculous nickname she expects my little boy to run around calling her, which wouldn’t do him any favours when he gets to school. Whilst in the car with me and DP she starting talking about how she’s still having periods and could easily still get pregnant (she’s only 50, DP didn’t know where to look and commented on how strange it was), she’s insisting she hates every name we come up with and has a list of about 5 horrendous names and when we say no she sulks and says she needs involvement in the name choosing and that we need to adapt his middle name to her name!! the latest one has been discussing child care and stating she doesn’t trust my DF to look after the baby and that his partner shouldn’t be involved at all and that she wants to take a year off work to stay with me and baby,to ‘help out’ take over .
The most worrying thing is im having a boy and I’m my DM’s only child (obviously female) and she has always told me throughout my life she always wanted a boy and when her sister got pregnant with my cousin (boy) she stopped speaking to her for ages through jealousy and said she had taken the life she always wanted. We had a gender reveal and When we found out it was a boy you can hear on the video she took that she was sighing. I may sound neurotic but I’m adamant she’s jealous. a few years ago she asked to have said cousin overnight (aged 6 at the time), she had agreed to return him to my auntie at a certain time the next day, the certain time came and she had turned her phone off and taken him out all day, my auntie clearly going out of her mind and my DM didn’t return until around 4 hours later and acted as if nothing had happened. She has also done similar things recently with our dog (I know I know it’s a dog, it’s the principle please hang in there!) But she’s insisted on me giving her a key so she can take him out and then we have returned home 2 hours later expecting her to have walked him and gone, yet got home to her and the dog gone and us waiting around (actually missed an appointment) and she had turned her phone off. Rocked up 20 minutes later saying she had taken him on another walk as he was crying (hasn’t cried since he was 10 weeks old, he’s 10 months old now) I think it’s a power thing. These are obviously a few examples and my DP has agreed as great as she is with kids, he’s worried she would do something stupid like take him out for the day pretending he’s her son and then not return back until 10 pm at night or even just take him back to her house overnight and just not tell us, then make up some excuse as she always does.
Thank you if you’ve got this far!! My AIBU is that I’m actually worried that she will start to take over from the start basically with the baby, I know I’m going to need help etc but I’m a VERY independent person and have OCD and this baby has been longed for after a lot of heartache. Not to mention my DP is amazing,will be so supportive and is already very hands on with his other 2 children etc, and I’m possibly going to be out of it and not able to voice my opinions to her at the birth , ie could you just not hold my baby first as he is you know, my baby (she has stated if I have a EMCS or I’m too ‘out of it’, she could be first to hold him) and I just know she would start bloody shouting at the poor midwives if she wasn’t happy with something. Generally I’ve just changed my mind and think I would rather me and my DP only! (I’m private anyway and having my first baby is massive and me and my DM aren’t thick as thieves like other mother daughter relationships)
I just want some advice about how to go about this without her massively kicking off. She will anyway in one way or another, but AIBU or do I have every right to say well actually I’ve just changed my mind and want just DP there with not much more explanation than that?
Please don’t jump on the ‘she’s your mother don’t be so rude when she’s offering help’ bandwagon because her favours always end in more stress! Just here posting for advice and support really (if anyone’s got a difficult DM or MIL?!)
Thankyou for reading all of this!