Hello thanks so much for reaching out. He's incredibly supportive and I think this will be the case. I just want to feel the excitement instead of worrying. Appreciate the kind words of encouragement. 

Hi and thanks for taking time to read and reply. I changed all the names to make it easier to write. I still don't get all these acronyms. 
 

I feel relief that it's not just teenage stuff. Because she is now 12 and swearing and cussing at people. Alice is now 10 and so obviously I was worried she'd change from her kind natured self. 
 

I've committed to going on the trip. My partner supports me massively and I want to do the same. Although I have read through all of the comments and agree that I cannot and will not be left alone with her at any point.  He's a great dad and has also been put wrongly in the firing line with accusations although they were less damning than the ones I faced. He's just trying to be a good dad by not leaving her out and I feel so bad for him because he is hurting. We both tried everything and he even took time off work to try and find out what the root problem was. Therapy and psychologists did not help us as they have a confidentiality agreement so we have not once been told why she is acting like this. She no longer hits her sister like in the past but still continues to say hurtful things or try and manipulate her. Alice had a short term of therapy to enable to her to be comfortable saying no and standing up for herself which has been very successful and she is now her own person. Matt just wanted a great family life he's devastated at the outcome.  I term myself as a friend to their mother and have done everything to not be the "wicked stepmother" and feel I have a decent cooarenting relationship with their biological mother. 
 

I have always wanted to go and following some advice from a friend have tried to stop thinking of all the bad things that could happen and hope that just for one holiday, Samara will play nice. Even if it's fake I will take it. I desperately want Matt to have a positive outcome because i think it's crushing him. 
 

I'll take any advice on how to handle a SD (ooh I got one!) that clearly hates me when on a trip. It's been about 5 months since I last had to parent her so I am feeling a bit anxious even though Matt will be there doing most of the parenting. 

Hi and thanks for reading and responding. I have to admit that when he first mentioned she was coming I was a bit taken aback. However I know it came from a good place. Regardless of what Samara has done, she's still his daughter so I don't think he even considered her not coming. He wanted to surprise me with a festive trip to Disneyland as he knows I've always wanted to go (and so has he).  I wasn't going to talk to him about my concerns but we are honest with each other and in the end I decided that keeping it on steptalk wasn't the only way.  He has said that it's kind of a test-the-water trip. He's assured me that if she in any way disrespects anyone on the trip or is naughty that he will handle it and potentially not have her come on any future trips.  We are actually planning another trip just me him and Alice next year to do an activity that samara had actively said she wouldn't want to come and do so we are going without her as due to her personality we know it would end up being uncomfortable and a waste of expenses. He has also booked time away for us just the two of us. He explained he's hoping that she feels more comfortable at her biological mothers and that the time and space apart (Samaras choice, not ours) will have put less pressure on mine and her relationship. He could be right so I'm going to give it a try. I do think you're right about being prepared though I don't know what to expect. Matt thinks that she will be fine for the trip because she will be having fun and it wont be that day to day home experience with bedtimes, rules etc. I hope he's right though as I would like to have a nice time!

Well you are completely right. She was 10 but is now 12 and it has definitely got worse. I'm just relieved that I'm not the main carer anymore as she has moved back to her biological mothers. It wasn't feasible as Matt is often away for great lengths on ship and I was left to deal with that. 
 

I tried thinking of excuses not to go. But I'm not going to let her have her way and cut me out. She needs to understand that I am part of her fathers life and to like it or lump it. Also... Matt and I have gone through some very testing times because of Samara; and we are still very much in love and trucking on. I couldn't not go because he is excited to go with me as well as with the children. It would hurt his feelings and I don't want to do that. Now that I'm not dealing with it day in day out I feel that I should put up with it every so often. He's a great dad, and Alice is an example of that. I don't know what the deal is with Samara but it's not his fault. 
 

Do you really think it's psychopathy? She hasn't always lived with us and she is just a child. Despite her horrific actions I want to question whether there is an underlying issue or medical problem? How can both children be SO wildly different?