It does sound as if your MiL RedheadedMommy has some problems, maybe even illness.
I was fortunate and always had a loving relationship with my MiL and now, as a MiL myself a good relationship with my SiLs.
It is sometimes hard to imagine how or why parents/ grandparents get into these estrangement situations unless there is a mental health issue or a momentus event (theft/ physical / verbal violence etc) that would cause such a painful and irredeemable rift.
There are some people who, in any situation, like the world to revolve round them and their needs. I guess if a MiL or S/DiL were like that it would put a major strain on a relationship. No-one likes to feel they are walking on egg shells all the time... life is too short!
It is sad that the children fail to have a warm relationship with all grandparents. It can be so very special.
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