Thanks, everyone.
'Facts not feelings': that's good advice, momeraths, cheers. I do try to keep all communication bland, neutral and factual, as I find this an effective shield which it's hard for her to get through. Similarly I don't rise to her barbed comments.
I'm not too fussed about her visiting with her husband, as he's fine (the poor sod) and she's much, much easier to deal with with others around. It gives her fewer opportunities to isolate me, and it keeps the craziness in check. She has been here before, when she invited herself for three days. She'd offered to do something for me with the house which I really needed doing and couldn't do myself, and which she was offering as a Christmas present. I can see now, of course, that it was another obligation trap to make me feel like I had to say yes to her visit (because why would I say no, when all she wants to do is come down and help me out . . .?) It's very clever, but I swear to God it's not conscious on her part. Subconscious, yes - but I don't think she actually sits there and plots. She's just crazy, lonely, and has no conception of healthy boundaries or relationships.
Hissy: the problem is I'm unemployed at the moment and don't have children (we've been trying, but only MCs so far). I spend most of my time renovating the house we've just bought. Thus she knows I'm at home all day, most days. It's hard to make the case that I'm too busy, especially as she'll then offer to come and help with DIY. I can 'create' things I'm doing, but I'm just sick of being the one who's on the run, having to think up lies about why I don't want to spend 48 solid hours alone with her.
That's just the irritation talking, of course: I know I'm going to have to draw the line somewhere, whether it's by stonewalling or lying about being busy.
Attilla: I meant that she displays traits of borderline personality disorder. She certainly does 'I hate you - don't leave me'. I feel a lot of the time like she hates me, but she's desperate to get into my skin. It's a terrible combination.
I can't remember why I resumed contact. It was five or six years ago now. I think she seemed to change, and to become less demanding. I read the piece posted upthread (sorry, can't remember who posted it) in which someone said that people will often change just enough to drag you back in, then start reasserting the old patterns, and I wonder if that's the case. A lot of that post rang true.
Nothing's been bad enough yet to make me go NC again. It's just this low background grind of resentment that drives me nuts. I'm always being got at with implications that I'm hurting her, letting her down, being ungrateful, and I just wish she'd f off.
If I'm honest, I do feel guilty. I can sense this tremendous sadness in her, and I know her own childhood was absolutely awful. She's told me the details (before all this kicked off) and it wasn't pretty. Her own mother was vile to her.
On the other hand, that's not my responsibility and I just want a normal mum, someone I can talk to and who will love and support and encourage me. I don't know how many people are lucky enough to have that, but I wish I was one of them.