That's well described, Betty Anne.
It may be she feels drained by your sad/stressed/negative feelings about your family. Or infected by your agitation or anxiety over them. I get that.
I used to drain friends like they were washtubs. Took me forever to understand that my emotions had an impact on people around me. It didn't mean I didn't deserve friendships.
But it did mean I had to intentionally find new additional (not replacement) sources of support, so I could spread around my huge neediness.
I stopped shaming myself for needing support. I just faced it. I really did. (Hey, I've been on this board for many years now!). But I started understanding that some people (whatever the label, friend/acquaintance/whatever) -- couldn't hold it for me or with me. They'd heard too much. My stuckness and repetitions of the same old agonies triggered their frustration.
They weren't mean. They were drained. So my task to to "spread it around" and find MULTIPLE sources of support because I needed a LOT. That's when I found a women's support group, got into therapy, went to a church, joined groups there where you could "come as you are" emotionally, did some volunteering.
With your husband's serious cancer now you may barely have time for all that, and you must be under a lot of stress. The time WILL come when there's room for you to find all the strength and support you need. Now may be more of a mental survival marathon.
But everything does change in life. Even marathons end.
So as you can, whenever you can, "spread it around" (a little venting here, a little venting there...and STOP venting with someone who's ordering you to not speak about something). Find all those other sources of support one at a time as soon as you can. Maybe a caregivers' support group. There are all sorts of things if you hunt some down. Your time may not allow much new activity, but take whatever you can into your routine that is support.
As to that friendship? I dunno. Only you can decide if on average, if it hurts more than it helps. It's awfully painful to let a friend go....but it also happens in most lives at one time or another. I've done it a couple times when something began to feel so stuck or toxic that I knew I should release relying on that person.
Have faith. Keep on taking care of yourself. Don't give up. All things change and the painful things will too.
Hugs
Hops