Maybe she needs see a councilor. It sounds like shes hit rock bottom and is just stuck at bottom of a hole. And needs guidence to get out.
If shes stuck in the house all the time she is just going to get worse. Take her out for a walk and spend time with the grandchildren. And keep reasuring her that life does get better after drink.. its just that 1st hurdle she needs to admit it and weather the storm for a bit. But there is always light at the end of the tunnel.