Hi yes I've been LC for a while. I've had bouts of NC at all. But I'm in contact now with her for my own sanity.
Erm. Worst things shes done? There's a long list. Completely blanking her 80yo mum who visited her in hospital every day for ten weeks. Her Dad told her she never wanted her and she deludely believed it. Despite my lovely grandmother who never swears or raises her voice scoffing and declaring "that's bollocks" when told.
She lies a lot and if you stay in contact with them you have to learn to grown a very thick skin.
Worst thing she's done to me? Ringing social services (it came to nothing) because she didn't believe DS was autistic - it was simply a case of I couldn't cope. 
Other things. Having a massive strop on the ward one day when I was in hospital very poorly (asthmatic). Reason for the strop? She hadn't been told. Reason she hadn't been told. The A&E Nurse rang her to say how worried they were for me and she told them she's going home to have her lunch first!
example of a lie they tell, my dear friend who takes no shit off no one, gave her a few quid to go and get herself a cuppa to calm down whilst she sorted me out, (I was in with breathing problems and was in hysterics after the outburst), she told her friends that my mate 'banished her from the ward'. She'd have deserved it, but it's not what happened. Deleting an entire piece of university coursework that was due in the next day because I hadn't asked her use her computer. That one took some explaining to the lecturer!
oh and ignoring her best friend who ess dying of cancer, she didn't believe she had it because of how quickly she deteriorated
even though we'd watched out relatively young uncle (in his 50s) deterioate and pass away pretty rapidly upon finding out he had lung cancer.
I find I have to be in a food place to deal with her as it can be emotionally draining. She's recovering from an op at the moment and i recently went down to help. She had carers in place with me not being 100% and the test of the family working days or nights, but she's already sacked half of them. I ended up going down and helping at her request. Did my back in. Made myself poorly by going out in the rain to get her shopping. Dropped her meds off at the chemist and nearly made myself late for school run. She text me when I got home to say how lovely it was of one of her church mates to pop by, not even a 'thanks for today pixies'.
My Dad has currrently banned me from going to visit at least until I'm better now! 
If you're going to stay in contact, dont treat her like a child she isn't, but do try to ignore the attention seeking bits. The attention seeking bits involve trying to start an argument too (bad attention is still attention) Google narcissism and enablers etc etc. I've found DM is at her worst when she's with her enablers. They're her crutch. They dont care about being called out, you wont change their view. They believe they're right and they're the victim and it's everyone else who is at fault. You'd just drive yourself mad trying to get her see the error of her ways.