I wouldn't say she doesn't want to do it with them, at least not before he accepts her feelings and confesses his own, but yeah, I can't really see this as netorare. Considering what we see and hear about her, she seems to have been doing this even before confessing to him, but as Xelgadis said, might end this once they accept each other and start an actual relationship. There's nothing to steal/NTR before this, though.
On the other hand, False ReRAPEtionship might qualify as NTR instead.