Partners ex wife following on socials

Have you had your partners ex partner/wife follow you on socials. I have met this person once, they share a child. It seems odd, we are both in 30's, always seemed that maybe young girls out of pettiness's would do it. Could it just be curiosity? This person doesn't even follow her ex partner on this social media. They share a child and are amicable/friendly for the sake of child.

I find this funny but also don't feel intimidated or anything. I guess just some people like to be in someone else's business.😅