From my experience from an in-law who tried to usurp my relationship with my children :
She is long gone ( died in the 1980’s) and fought tooth and nail to “claim and act as if my children were hers”! She would sabotage me at every turn).
( she had only one child and could not carry any more pregnancies, so therefore her Grandchildren were her saving grace to garner “acceptance” from her own aged mother and sisters who had several children .)
It destroyed our family ( divorce and alienated my children as youths and adults).
She used bribery by means of money and gifts and attention of which she had more money to do so.
In the end it was due to her husband s who rarely took time with her as a wife and thus she transferred all of her devotion and need to consume the attention on my children.
In short….take your wife somewhere to regain the relationship of a loving couple , before she causes a ‘divorce” and alienation and confusion of the children’s loyalties.
In my case I had a “mommas boy” as a husband that was compliant to her mothers need to control and take over not only his life but our children’s as well through bribery and knocking me the mother of my children down for over 11 years.
Don’t let that happen to your Granddaughter nor the “mother” of the children too.
Your wife is trying to displace the mother due to lack of attention from a husband who is bent on leaving things as is just to get some peace?
Take your wife out as a loving couple does , when the kids are not with her to remind her that you are together. as a couple.
Good luck I hope that the situation does not escalate to what happened in my case.
My prayers go out to you and your family that you solve this peacefully.