How can you help?

I'm sorry that you've found yourself in this position. Ending any relationship can be challenging, but especially when children are involved. It can also be complicated when the couple is currently living together and/or sharing expenses. It seems as though you have made up your mind and that you find that this relationship is no longer good for your mental health. And that's okay! You have to take care of you, and if this relationship is no longer good for you to stay in, it's best for you to start ending things. It's good, too, that you are considering how the split will impact her and her children's lives. If you are concerned about her life "spiraling" after the split, could you potentially help her in setting up the things that she and her children need to thrive? This could mean helping her secure housing, helping her figure out a budget, offering to help with any child care while she's setting up other options, etc. 

Also, if you are concerned about her alcohol use, another way to support her would be helping her find resources in your area such as groups or individual counseling. Let her know that you are concerned for her well-being and that you feel she would really benefit from talking with someone after the break up. If you feel comfortable, maybe consider reaching out to some of her close friends and family to let them know about your concerns. That way they can help support her after the break up. If all this comes from a place of caring and empathy, she will be more likely to move forward with getting herself help and accepting support. 

I know breaking up can be hard. Even though you are the one choosing to end things, there may be some adjusting on your end to work through. Take care of yourself in the mean time and find ways to give yourself support such as starting therapy for yourself, reaching out and talking to your own personal support system, and focusing on your own self care.

I wish you the best of luck!