So my DH has 2 11 year olds. I've known them since a year after we started dating and 1.5 years after their parents split up. So I've know them since they were about 4. They don't remember their parents being together and up until now I've had a good relationship with them. There is always an underlying current of antagonism from them towards both my DH and me and it feels like we both have to walk on eggshells with them because their mother is manipulative and emotionally abusive towards them and she's done a lot of parental alientation. They used to stay overnight (mother was distraught at this) but for the last 2.5 years one of them has refused to leave her mother even to visit friends (mother claimed it was because she had separation anxiety from her mother, then it was because DH was a bad parent, the GP thought it was because of the conflict between her parents and recommended counselling but the mother wouldn't allow it, and then after months of emails to and fro between mother and DH, mother decided that actually SD1 had high functioning aspergers and any attempt to help her would be damaging). A year ago, after much pressure from her mother, SD2 stopped staying the night with us although she'll spend nights away with friends. Since then every other weekend has been a succession of pickups and dropoffs, with the girls being really hard work for an hour or so around each handover at the beginning and end of each day. 

But considering all that, my relationship with them has been ok, and they absolutely adore their half-sister (my daughter) who is 3.

A year ago I touched SD2's hand in a conversation and SD2 told her mother that I had hurt her. Mother then changed this to I had "physically disciplined" SD2, which according to her email is something mother and DH have never done (trying to cause conflict between me and DH by making me the bad one. Didn't work). They've never had that level of agreement about anything since I've known them either. There are various reasons relating to her mother why I believe SD2 said this, so although it worried me and hurt me I put it behind us.

Then just before christmas out of nowhere I managed to antagonise SD2 who then in the ensuing tirade said I'd hurt her (again). Again I don't think this is the case. I think she was hurting emotionally from things that were going on at home (mother has been being quite vindicative towards her recently and maternal grandfather is quite ill - we didn't know this at the time) and I think she just wanted to use someone as an emotional punchbag. The next few visits were equally fraught, with SD2 just having a go at me and nothing would stop her. 

On top of this since all of this kicked off my 3 year old SDs half sister, started saying that mummy, daddy and SD1 are "bad guys" and SD1 says "not nice things to daddy", which is true. I don't know where she got the "bad guy" phrase from. Either from her sisters or because of the confusion caused by someone she adores being mean to someone else she adores and the ensuing tension.

As a result of this I've taken myself and my daughter out of this situation and we've made other plans the last 2 weekends we've had them. OMG. The relief is beautiful but it's not a long term solution.

What concerns me most are the accusations of me hurting SD2, particularly as the mother is a pathological liar and even if her lies are discovered she doesn't care. It's just like water of a ducks back. Which makes her very dangerous.  She thinks she's untouchable. Which she pretty much is. SD2 doesn't realise the devastating affect these accusations could have and she's fiercely loyal to her mother.  But these accusations are putting me (and therefore my daughter) in a really vulnerable position.

Any suggestions?