It's not you. I would have been furious that she cut my son's bangs. As you pointed out, this is not the first time she's done this and if I recall, you've had this discussion before. I think what needs to take place is that if she's going to discuss the matter w/your h, then you and your h need to decide together about your son's hair cuts. Granny likes control. She may think she's helping you out, but it's about control She knew that if she cut them too short, then he would need to have his hair cut. Think about how that child might have felt going to school and being teased about it. That's not a good thing.
I wonder how she would have felt had you gone over and noticed a long hair and snipped an entire clump from the front of her head just trying to be helpful? She wouldn't have liked it.
If granny can't do as you have advised her, then granny day will not take place. Plain and simple. She needs to learn to learn that she can't parent other people's children and do what she likes w/the children, i.e., cutting their hair. That's not her job nor was she asked to do so. Stick to your boundary and maybe she'll think twice about this after a few weeks of not having granny day.
Sit quietly, the answers will reveal themselves when you least expect them to. The past is gone, the present is a gift and you need to focus on today, allow the future to reveal itself when it is ready.
