I'm going to go against the grain here and say that I really like Facebook and think that overall it's a good platform with some flaws. Right now I'm messaging 2 different groups and about 5 different people, while organising an event that's happening in a few weeks, and organising supplies and camping for a festival on the weekend. After this festival in the weekend, I can post the photos I took on Facebook, where e…
You could have turned off seeing updates from her. That would not solve all the things you mentioned but it should in almost all cases suffice.
Friends giving each other space is maybe a thing but not being able to handle seeing her name pop up at all is a very extreme state of affairs about which I would suggest consulting with someone.
I think it's unfair to expect a feature that caters to that. You cannot just full ignore somebody in real life either, e.g. friends mentioning her name.
Facebook does in fact allow you to block a person or unfriend them. If you and your friend are in agreement about giving each other space, those two options should be enough from a reasonable feature expectation standpoint.
If you are friends with someone and interact a lot it's obvious and generally a good thing that Facebook highlights them. Facebook cannot know on its own that you are currently "not actually" friends with someone.