Background: my mom is a single parent, she had me fairly young (22). We lived with my grandparents most of my life and they served as parental figures. My grandmother passed away when I was 12, it was very hard on me and even harder on my mother. My mother and grandmother didn't have a good relationship and my mother never really dealt with her passing. Long story short, after my grandmother died there was a lot of moving around and ups and down on the part of my mom which I was subject to. I came to realize that I went through "parentification" where my mother treated me as a parent and leaned on me for things a kid shouldn't know how to handle.

I'm now 27 and haven't talked to her in about 2 years and have a difficult time dealing with the guilt. What led to this:

While I was in college my mother had ovarian cancer, being the dutiful daughter/adult, I was there for her for everything. She eventually decided to quit her respected job of 10 years while I was still in college. Normally this wouldn't be an issue except she being a single parent didn't have a lot of money, she took out her retirement savings and spent it all by moving and not even looking for a job. Her behavior got worse and she acted very erratic and very mean to me, the doctors thought she had bipolar disorder, later it was found out she has Graves' disease for which she needs to take medicine for the rest of her life. I worked my way through school so I didn't realize the extent of what was happening. My senior year of college I turned down a job offer in another city to try and go help her. She had been through several jobs not keeping any of them after moving, I was working 2 jobs to try and get by. She had ruined my credit at this point by continually using my name for things and not paying them. When I graduated and moved to help her it was a very dark time for me, with her in the hospital, no support etc.
Fast forward several years of this, ups and downs, jobs and no jobs. Me supporting everything as best I could being 21-24, but her not helping herself by doing the important things, like going to the doctor and getting her health on track. She wasted money on cigarettes and who knows? Always saying she wanted to go back to school and finish her degree, but never doing it, never applying or getting grants or aid.
Finally I came to a point where I was felt like I was drowning because of her and decided I needed my own place. She decided to move again to someplace several hours away knowing no one without looking for jobs or applying to the school she wanted to go to.
I'm not entirely sure what happened, but she was angry with me for letting her go and a series of her moving happened and craziness with which I couldn't deal with. I stopped talking to her and giving her money I didn't have.
At one point over the years she was doing ok, she found a place and had finally started with school, she was evicted and had to move into my grandfather's wife's house, which is under foreclosure. I'm certain she is still not getting the medical attention she needs.

In this time her father (my grandfather) helped her very little, I'm angry with him about this for putting it on me. He at one point offered to take her in (he lives in another state) but she wouldn't go. During this time of not letting her consume my life, I was able to get my life together and get on the right track.

I feel guilty now because I want to help, but I can only help a little and that is never enough for her. My grandfather doesn't help her, but she needs it. I enabled her for years and when I stopped she failed.

I can't have a relationship with her, it's too stressful and all negative, and now I'm sure it would be worse because I stopped helping her to help myself.
I feel like I've grieved over the mother I'll never have and I know I shouldn't be responsible for her at this point in my life, but I have a hard time still accepting that.

She will have to leave the house she's in in a few months, at which point she will be basically homeless. I have suggested she go with my grandfather, but he doesn't want that. She's tried for social security but who knows if that will ever help her. I live in another state now with my boyfriend who's been there for me through all of this.

I could afford to buy her something small like an rv or mobile home to live in. But I'm afraid I'll open Pandora's box and it will never be the end, since it's all or nothing with her. It's also her 50th birthday coming up and I know it's a big milestone that I feel bad about. My aunt spoke to her on Christmas this year and said she was doing terrible, that spurred me back to feeling badly about it. I get frustrated that my family talks about how bad it is for her but no one does anything. It's like they know I tried and was unsuccessful with her, so they don't try at all. I can't keep trying, it would mean I would be sacrificing my life, career and happiness, for hers.

I don't know what to do.