Yes, those terms describe my mother too. I have spent a while trying to get over the way things were when I was a child, and thought I'd made a lot of progress, but then little things like this crop up that remind me that maybe things are a bit deeper than I realised.
I do have to remind myself that I am very lucky to have a great relationship as well as my marriage - I had already told them about stepping back before the original post, with the reasoning being mainly that she's otherwise single - I have a husband, family, full-time job, and other commitments and this just feels like the right course of action.
I think at some point I will have to speak to her about things - I'm hoping if I can pin my discomfort on her behaviour rather than her character we might be able to move past it, but I'm aware from dealing with my mother and other similar people that I can't necessarily assume reasonable behaviour and a straightforward conversation
Thanks again for your replies, I'm definitely enjoying my first 'proper' poly experience - it just seems very right!