I'm with you. I don't want to judge her because I have never been, nor hope to ever be in such an awful situation of losing my spouse, especially under such circumstances. Everyone has a different opinion on how long one should start dating after grieving. Seven months does seem a bit short, but again, I don't want to judge. So long as they are not hurting anyone, do whatever with it is that will help you deal with the coping.
There are four grieving children involved. They are hurting, and a new stepfather and their mother's preoccupation with him is NOT helping them cope, believe me.