You aren't alone here. There are several of us with similar stories. My BPD mother has passed away. My father, who also enabled her, passed away several years before her. I also was expected to be the strong one, his- co-enabler.
Dad's passing was difficult- I know it was for you too. It's a huge loss. Our extended families lack the capability to be of emotional support during this situation.
In addition to counseling- I also did this since college, I found ACA groups and CODA groups helped me to let go of some of the feelings of being responsible for our disordered family members. However, this gets complicated when a disordered parent is elderly, because, elderly people can be dependent on others. The line between when to help and when to have boundaries is not always clear.
You aren't alone with this. I think we try to balance boundaries, our own emotional well being, while also feeling the obligation to help an aging parent. My best description of this is like walking a tightrope- sometimes it's a balance, we sometimes wobble, fall to one side or the other. All we can do is the best we can. It's imperfect. Guilt is a part of that, but FOG- Fear, Obligation, Guilt- is also part of the roles in family dysfunction.
I have posted this article. It may not be the exact situation but the emotions are similar.
https://slate.com/technology/2022/03/mentally-ill-parent-elder-care-boundaries-liz-scheier.htmlSome of the guilt may also be grief. Grief that this isn't the kind of relationship we wish we had.
First of all- you are not required to sacrifice or jeapordize you or your own family's well being for your mother's situation. On the other hand, if you wish to do something in support, then that is your choice too.
Are you in the US? It helped me to meet with an elder law attorney to learn the resources, such as what Medicare covers, Medicaid, power of attorney if you wish to pursue this or not- there are pros and cons to that. If no one wishes to take this role, the state can appoint a guardian in the event your mother isn't self directed.
Depending on your mother's financial situation, or mental state- she may be eligible for some kind of services like Medicaid that may help cover needs like nursing home care or some home health care if needed. It helps to be informed, even if these resources aren't needed or used, but to be able to have an idea of what is available or not.
It may be that you don't need to consult an attorney and take on that cost. In the US there are organizations like the Council on Aging that have volunteers who can meet with you and explain what is available and who qualifies.
Although my mother had BPD, she remained legally competent and self directed, so she made her own decisions. She did not qualify for some resources but it helped to know what was available for her.
You still can make whatever choices you wish, but I found it helpful to learn what was available. Keep posting here- and there are others who can also add their advice.