Sorry for being late to the party but this reminds me so much of my MIL I couldn't resist. Like has been mentioned before, people of this nature are often very loving people. They really are nurturers and caretakers and put a lot of stock on their ability to see themselves as good people on how much they are helping others. But like my MIL, sometimes that ability to be seen as a nice person deteriorates into controlling behavior because you can't be a good person helping others if no one is asking for help. So you start pushing to help even if it's not asked for, you go around other people's homes looking for things to improve so you can "help", you take that person not being there as a way to improve things around the house such as cleaning or tidying up and yes that also involves "helping" the children sometimes by directly counteracting what the parents want for that child.
Of course with help also comes the ability to control others because the more people rely on you for help the more power you have in their lives. Eventually you start to be unable to perform basic tasks without them (my FIL can't fill up his own gas tank or use an ATM so my MIL has to do it as her way of "helping"), you involve them in every decision you make about everything from which dentist to use to what carpeting to put in your living room as they can offer advice which becomes intrusive eventually because although it's great to involve someone once or twice in a decision as they can offer meaningful advice, you don't want to involve them every time but that's what it becomes.
The only thing that works with my MIL (and yes I am the one that posted on the forum a few weeks ago about my ILs not coming to my daughter's party as they weren't invited to come on the actual birthday as it was immediate family only) is to involve her in our lives as little as possible. I stopped telling her about things that needed fixing or being done as she would jump in and do them without asking. We bring our daughter to see her often but not necessarily every week and I prefer to do it at their house so that we can leave when we want and they can't go through our house looking for help. I have started to refuse help even in cases where she didn't ask if we want it (i.e. "I'm going to wash your sheets while you're away. I tell her in these cases that I'm fine instead of thanking her because I didn't know how to tell her that I didn't need that done). The ONLY thing that works is to create boundaries and involve her as little as possible. The more info she has, the more she inserts herself into our lives. The more she is in our home, the more she can suddenly start to help when it's not necessary. I still have a long way to go. It probably sounds cruel to involve her a little less in my daughter's life than she was before but I remind myself that this is the woman who reads through her children's personal emails without their knowledge and who cleaned my home and rearranged my garage without my permission. Perhaps it's better to not have such a manipulative, controlling and boundary disrespecting person in her life. Sometimes just because someone holds the title of grandparent doesn't mean they are always the best influence or are able to be the best teacher about how to live life.