So sorry to hear that you're having a hard time with this OP, but please try to focus on the fact that there is a 'grandmother-like' person available your kids...I would love to have someone to fill that role for my children (ages 5,6 and 8). From my perspective you are soooo blessed.
We seem to have more than our fair share of grandparents...all of them local, but not of them available. My husband's dad is was an awful father and would probably be an even worse grandfather, but we'll never know because my husband wants nothing to do with him. His mother is ok, but aside from holidays she is totally uninterested in our kids or being a hands-on grandma for them. My mother is mentally unstable much of the time as her polarity teeters between extremely manic and comatose. Having her around my kids would not be healthy for them so visits are very few and far between (and only for brief, supervised spells). As a result, my kids really don't know her as a grandmother and due to her mental health this will probably always be the case.
My dad is mentally stable, but has been struggling with serious health issues for the last several years and is just not physically able to be an active (or even inactive) grandpa. He is married however and I thought me and my stepmom had a good relationship, but she has been deliberately absent as a grandparent for my kids since I delivered them. She never calls to talk to them and on occasions when they have accidentally called her from my cell phone she responded with irritation and annoyance. She has been to 2-3 birthday parties total, she never asks to see them and the last time I told my dad I was stopping by to visit she ignored the doorbell and didnt let us in (my dad had gone out with a friend, but stepmom's car was parked outside the house so I knew she was home and she knew I was coming over). She has told me at least twice that she doesn't really like "little kids" and she does better with older, more independent children

At this point, I barely speak to her, so if I had someone who was enthused and willing to step in to grandparent my tykes I'd be over the moon.