I'm very amicable with my ExH. In fact his girlfriend has just ended things with him, citing me as the reason. Apparently she wanted all drops offs and pick ups done in a neutral location, such as a McDonalds car park, the DCs to only see him every other weekend and she expected us to never speak any more.
I speak to him maybe twice a week and it's generally about the children and arranging contact times or discussing their welfare. He has a text here and there, yes sometimes they were chatty but I never ever behaved like this ExW above and I would never dream of reminiscing about my time together with ExH in front of her. I do my own DIY, but I may ask him to lift something heavy if he was here to see the DCs but I'd never do even half of what she seems to have done and is doing.
As I read more about this situation, I personally find it a little too intimate. I am all for amicable co parenting, it is great for the children and my children really benefit from it and we do still take them places together sometimes. I wanted to be friends with his gf, so she'd feel included not excluded. She didn't want to.
I don't know, it just feels a little inappropriate, in this instance. The boundaries need adjusting a touch. I would feel a little threatened; they almost act like a married couple still, this paragraph made me think that: "This also covers things like visiting or helping old friends together, i am invited sometimes but not always. She takes an interest in his home and loves choosing curtains/cushions etc and buying them for him, things that she would have done when they were married."
If he cannot see how inappropriate that is, you do have to question how long you can put up with this tbh. If you are always involved and feel part of it and comfortable, then that's great but I don't think that is the case. It does feel almost a deliberate action on her part but perhaps it's subconscious or habit after all those years together. Co dependant does seem a good word to use, as others have said.
But then I am also in the camp that my partner shouldn't have female friends that they are too overly familiar with. That was how my ExH's affair begun though.
What a long and jumbled post. Sorry.