thanks llleee. This is really good advice, my mum is visiting this weekend so I will discuss it with her. I will google boundaries, I think Ill also google how people deal with distancing themselves with family members, and how they go about it if the person involved is trying to contact them consistently.

I feel at some point I will need to discuss her behaviour with my sister, maybe not right now whilst she is living at my mums, I dont want to make the situation worse.
My mum was talking about getting my god father (who is old but quite a gruff-but-caring and rational person) over to evict her in worse case.

I will talk to my mum too about how she can keep herself safe and enforce boundaries herself. For example, my sister likes to talk A LOT, but after a long week of talking, as a solicitor its mentally draining and the last thing my mum wants to talk about is seemingly petty problems over and over. - I suggested last time I saw her she makes like a rule book and as childish as this sounds, my sister obviously needs concrete boundaries that my mum can raise as a solid point when things get bad to refer to. (literally just wrote this as a text came in saying she had been working 13 hour days and has asked my sister not to talk to her this weekend, and shes already been bugging her despite this!)

I will ask her to come round mine if she feels threatened or is abused. Im only a 5 min drive away.

Sorry the post was so long, I felt although I didnt go into earlier past stuff, a little background on her behaviours within my family over the past year especially was needed so that it didnt seem like I was making a fuss over nothing.

Im off to read up on this stuff, thanks!