Thank you for sharing this. I have to think a bit and process my thoughts before I reply with further insight. I was in a similar situation with my parents and my older sister, so just letting you know that I can relate to your story and maybe we can both learn from the experience you have shared.
Don't lose hope. You are not a terrible mom. Saying that is like condemning yourself for being a human. We are allowed to be human right?
Take some time to cool off. Go for a nature walk. Put those sad thoughts to rest and revisit it later upon reflection. I know it's harder to process things when emotional. Hang in there!
*hugs*