Anyone ever posted on a Facebook group only to find a relative is on the same group?

[phoenix1973]

I was on a group and I noticed a new member had posted. Opening up about issues that are upsetting them.
Fgs, it was my Mum!
She also found one of my responses to another post and put" its sad that I find out more about xxxxx life on here than irl"
I was mortified.
Anyone else had this happen to them?

Should imagine it's quite a common occurrence if the groups are local. I'm sure some people think Facebook is private to them, when really whatever they post is very very public.