I don't know why it's anyone's business. I'm sure if the two of you had some work to do where you had to communicate- you'd keep it strictly business. So if you don't- there's no reason to seek her out at work and have an update on your life outside the office.
People who haven't experienced being closely connected to someone with BPD don't get it- as the pwBPD often can hold it together in a more public, less close situation. So I don't even try to explain, it would just reflect poorly on you if you did.
Maybe a reply if they ask "I just want to keep my focus on the job" is about all you can say and hopefully they will just let it go.
It sounds like you are doing some self care- not drinking, keeping a healthy weight and investing in your own well being. It's good you are doing that.
If I absolutely had to, yes. But me and my immediate boss and service chief know that isn't real. So I just avoid. Maybe one day? I'm unsure how. It became a giant deal at work. They'd be dumb to push that.
I have no need or want to update or talk which is why it's annoying that people act like I should do that.
My response is "I simply don't want to be around her".
I'm doing as good as I was before her. Very fit. Focused. I just don't want to explain why it makes sense why I don't want to give her access to me. They don't know or see "her". Although it's coming to light.