Helping an Adult Daughter

I’ve been told by some wise people over the years to let go of my attempt to help my 35 year old daughter whose life has been in chaos for 20 years. She has gone through the usual: addiction, failed/disastrous relationships, poverty, etc. It would be easier for me to let go if there was not a child involved. My seven year old granddaughter has been through more than any kid that age should have to endure. They are now homeless again. I’m at a loss. Any guidance would be lovingly received. Thank you!