You are right to be concerned. Your friend and her son are in danger. The so-called boyfriend is often drunk and violent and he emotionally blackmails her by saying he’ll kill himself if she leaves. She is stuck and afraid for herself, her son and her dog. She also doesn’t want to feel responsible for his death. She needs to get out. But she needs to do so safely.
You can’t expect yourself to know what to do. All you can do is love her and point her in the right direction. She needs to be in touch with the National Domestic Violence Hotline. (thehotline.org). Counselors are available for online chat 24/7. She could also call them: 800-799-7233. They can help your friend sort out what she needs to do and can refer her to local resources.
Do tell her to not use a computer the boyfriend has access to. Men like him often get violent when they find out that their partner is looking for help. Let her use your computer or one at the library.
Has your grandmother agreed to let the family use her house? If not, that’s going to create more trouble for your friend and it will damage your relationship with your grandmother. Be careful about making offers like that unless it is okay with everyone involved.
Your friend is lucky to have you as a friend. Give her the hotline number and just be there for her.
I wish you well.