Why are my ex’s friends asking me questions about my dating life?

Ex’s friend: (randomly) Do you have a girlfriend?
Me: *tries to dodge question and change topic*
Ex’s friend: *goes back to topic of my love life* So does that mean you have a girlfriend?
Me: Yes.
Ex’s friend: How long have you been together?
Me: We’ve been talking since October
Ex’s friend: *continues to ask a lot of questions about my girlfriend and tries to find her on IG to see what she looks like*

What the hell is the point? I never talk or ask about my ex around mutual friends and I don’t concern myself with who she’s seeing or having sexual with. I’ve blocked my ex on IG and her phone number and quite honestly, I’m tempted to do the same with her friends. Why are her friends concerned about my dating life?
Updates
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Backstory: My ex and I used to work together. We dated until I found out that she had a long-term boyfriend. I ended things with her and she decided to flaunt her long-term boyfriend in my face. I blocked her number and social media and stopped talking to her. My ex’s friend decided to confront me about why I’m not talking to her and how my ex is butt hurt that I’m not talking to her. My ex keep trying to get my attention at work despite me ignoring her.
Why are my ex’s friends asking me questions about my dating life?
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