"It also lists the SM's internal feelings as a 'symptom' of the 'syndrome'"
ArsenicyOldFace I totally agree. It seems to me that the 'miniwife' term is almost entirely about negative feelings a step parent has about a child. Which to me is not, at all, the point of a label - a label is about understanding, and finding strategies to combat an issue. To me it would be analagous with calling ADHD 'pain in the ass syndrome'.
I also totally agree with what PausingFlatly said about burdens.
The more I've read of this thread the more I feel like I probably had some of this going on as a child, definitely with regard to the emotional support of a parent.
I personally don't think I see it as automatically deserving of being called abuse, maybe because I'm not sure that the effects are all negative, or because I don't feel I was overly damaged by it - though I'm sure in some cases children are.
There are negative aspects, sure, and definitely one of those would be a difficulty adjusting to the arrival of a new partner, but I guess I feel that my definition of 'abuse' would be a relationship or action that always causes damage, and causes vastly more damage than any positive benefits. Not saying that spousification/parentification couldn't be abusive, but I would see that more as a variation on emotional abuse, and likely to be in tandem with other forms of same, from a parent who is struggling in many ways - there was an example above, I'm sorry I can't remember the poster, where it sounded like the mother there was indeed abusive, and used this as her method, but I do think that would be quite rare.
The thing is, I think it's not uncommon that a child might feel jealous of a new partner. And they might handle that feeling badly, and act out, especially if they have been placed in a position of responsibility that they now feel is threatened - they might try to cling onto ways of being that they feel are 'safe' and that have previously been rewarded. But they are a child. So it's up to the parent to work on problematic behaviour. And if the parent can't or won't, that simply cannot be blamed on the child.