How is Editor able to edit posts without logging in?

Need to figure out if this is a security issue or what is happening.

I have 2 bloggers editing posts on my blog. They both have user names (editor credentials only) and passwords.

Only one of them I can see daily logged in with his Ip and his user name.

The other one edits posts daily too but when I check my log under her user name the last time she was recorded as logged is a month ago.

I also check my login stats on wordfence. Same thing. Her Ip or user name does not appear in my logs

I am not a technical person.

So please someone help me figure out how she manages to edit posts, save drafts and so on without signing into my dashboard.**

would other people have access to my site as well?

I have also the Ultimate member plugin installed (subscribers), but these are the only 2 editors I have.

I don’t have any plugin that would allow people to post without login in