Using "stepchild" for ease although DP and I are not married.
DP is a fulltime Dad to 3 (he is a widower). Have been in a relationship with DP for 2.5 years, and been spending time with the kids for 1.5 years. All has been well, stepchildren have never seemed to have issues with me and I've always thought I must be one of the lucky ones. But recently DSD7 has been a bit off. Nothing major - but she has gone from wanting to spend time with me to ignoring me, or making slightly sarky comments, repeatedly asking when I am going home etc. The past 2 times that we have been together she has suddenly become "ill" - DP says she was fine before and after I was there and thinks it is to get his attention / concern. There are other little things like sitting next to me on the sofa then saying I need to move as her Dad is going to sit where I am, despite there being space on the other side of her and a whole other sofa she could have sat on. At times she is perfectly pleasant to me, but then it is like she has forgotten herself, and will randomly say something a bit off.
Mentioned it to DP and he seemed to think all was fine, and said we will see how it goes next time, when we have 4 days together.
Just looking for advice on how best to manage this if it recurs. She gets a lot of time with her Dad even when I am around - we have been very careful to ensure that - and often quite a bit of alone time as I entertain the other 2 SC. We are also conscious of the little things e.g. DP would never sit next to me on the sofa if one of the SC was sitting on the other, he would sit with them. Should I be actively trying to engage with her such as asking her to do something with me alone? Should I step back from her for now? Is it worth DP chatting to her?
I may be making a mountain out of a molehill but it really upset me as we have had a lovely relationship so far. It's also baffling as nothing has changed that I can think of to cause her to behave differently.