marthams,

We can speculate how she got that way, I suspect from her own upbringing by those who raised her.  Regardless, it does not really matter for she is this poorly behaved.

Please recognize that anyone who acts like your grandmother is a person of anger, spite and bitterness.  Anyone who handles family issues by not speaking to the other is someone who is immature and does not know how to really love.

Can you see this about her?

My take is that you have nothing to apologize for and even if you did that will not change your grandmother’s poor behavior or how she conducts herself in the future.  I see her repeating her silent treatment for the next minor infraction that she perceives that was put upon her.

How to cope?  Ignore her.  You cannot change her and she is toxic.  My rule is to stay away from toxic people which includes family.

By the way, congratulations on your new home!

Mark