Oh Mel, don't blame yourself. It's not your fault that your Mom had the accident. It's also not your fault that your Dad is cheating and your Grandfather isn't doing well.
Sometimes life just sucks.
You aren't a bad daughter. You have issues and you are only asking for help, whether you realize it or not.
Just do what you can to help your Mom get through this but don't blame yourself.
Wishing you the best.
Hugs,
Linda