In this case, it's different because she's not serving the dom in question - she's just following an instruction from him... I'm not sure why she would be kneeling before someone she isn't serving at his request, but...
Maybe, she's trying to tell you that she's not in a formal situationship with the dimdom in question - some doms do get a bit carried away and issue instruction to subs that aren't theirs. If she's a sub in the right mindset, she could be following instruction without thinking about it. The question is:- How far does it go???