Girlfriend wants to move back with ex for the kids

Going to try and keep this brief and give all the necessary details 25 year old male I have been dating a single mom of 30 with 3 kids of age 8 4 and 2. We don't live together but have been dating for about 6 months. She used to live with the father of the kids but he is an alcoholic and had hit her on multiple occasions until I met her. She is now working, and receiving government aid, but no child support from the father because she refuses to take him to court. She is living with her brother and sister in an apartment. it is her brother his wife and there daughter, and her sister, sisters husband and newly born baby. Lately her sister and sisters husband have been fighting about the behavior of her children. The 4 year old boy does not like to listen to anyone. They say she is very distracted at times and needs to be more attentive with the kids. And it is for that reason today she called me and told me she was going to go back and live with her abusive ex boyfriend. I told her that is not an option and will cause more problems then solve them. I don't know what I can do to help her because I live with my mom and sister and help them pay for our house as well.