My DS has a daughter and his wife is her stepmother. They never use that terminology for his wife, though. She and DGD have gradually forged their own relationship; there was no pushing to make them accept each other.
We accept that our DiL is not her mother and don't expect her to behave as if she is. She still cares for and about her and they get on really well. DiL's parents understand that there are 'real' grandparents and, while treating DGD like a grandchild, they are sensitive about how they do it.
US troops forced to act on the ground?

