how can i know who are following me on find my friends?

I have the same issue. Cannot remember exactly who I gave permission to follow me.

The support article you reference is not helpful on that point.

Any way to determine who is following me on Find My Friends?

The only people who can follow you are people you've given permission to. Are you saying you don't remember who they are?

See these articles for more information:

https://www.apple.com/support/icloud/find-my-friends/

See this article:

Find my Friends: Remove friends