You are not being too hard on her.
When you become a parent you lose all those rights to people making an exception for you.
You find that you have to put someone else before yourself.
Your mother couldn't do it, because SHE was inadequate, not because of you.
You have survived that and managed to step up for your own children, in spite of having no role model to follow, and that makes you amazing and wonderful.
You have every right to be angry with her. But you owe it to yourself to move past it.
You can't do that until you work through it - and talking about it is the best way to do that. So please, keep telling us how you are feeling.