My father was diagnosed with Stage IV colon cancer in 2007. He died in 2010 at the age of 60. I was 25. He too had multiple surgeries, chemo, radiation, etc. While we here in Canada don't pay directly for treatments, there was the cost of missed work, medical supplies, and the like. The following is directly, and deeply, informed by my own very personal experiences with cancer:

Let her die.

Chemo isn't going to save her, and it sure as hell won't improve her quality of life. It will give you maybe an extra year to watch her fade away before your eyes, and will inflict all manner of pain and discomfort on her in the process.

Your mother is going to die, far sooner than either of you would wish. That's unavoidable. What you do have control over is the quality of her life in her last few months, and in the effect that her passing has on the people she cares about. You can control how you spend what time you have left, but you have precious little control over how much of it you have to spend.

I'd suggest reading How Doctors Die[1], a take on how those who have the most experience with cancer and its treatments choose to deal with it. Generally speaking, they don't.

I'm sorry if this sounds harsh, but I watched my stepmother tear herself apart refusing to accept the inevitable and pushing for every last available treatment. The extra six months or so that may have afforded him are not a six months I would wish on anyone.

You are going to lose your mother, and it will break both of your hearts. Pumping poison into her and bankrupting your family won't change that. Make your peace, and let her go.

[1] http://www.nytimes.com/2013/11/20/your-money/how-doctors-die...