Radhead asks the $64 question: "How do you handle an unresolved relationship or friendship issue from the past?"
What I do is Plan, before I see this person.
Most of my Life is spent with people who are OK-enough for me to be around.
When I am with these people, I don't usually get "surprised" by what they do (and say).
So, I can Let Go of my fears, and be "myself" with them.
Then comes a day when I must be with a High-maintenance person.
Most of these people are on eternal Downers.
The day before a visit, I plan how I want to be.
Then I think of topics for conversation.
I may write-out several things I want to say.
As I meet her, I am relaxed.
I can truly give a warm smile.
I create a Mood for myself.
I bring-up one of my topics.
Over the years, I have done quite well.
Usually, the visits are OK.
This is certainly progress, because they used to be mostly hair-pulling sessions.
Each person has some warmth in them.
The trick is finding ways to find that warmth, and bring it out.
So, Radhead, if you really want it, you might get it: "Speaking to the person about the most mundane thing would help, even for just 30 minutes, but I don't know if the person would even be willing to do that for me."
If you can think-up 30 minutes of mundane conversation (and maybe steer her away from black-holes), then you have the possibility of surviving those first 30 minutes.
Good planning can bear good Fruit.
And, you are not just helping her, you will also be helping yourself.
She may want to actually have a few minutes of quiet talk.
And you can be the catalyst for that.
If this works, then you can easily get past those unresolved feelings.
Because those feelings are about the Past.
If the Present gets better, then the Past loses its grip on your mind (and spirit).
Good luck.