Yeah that's a tough situation to navigate if you know the other person isn't a rational actor.
In my experience, you have two real options:
1. Add no new information
2. Add new information as unambiguously as possible
I've personally found that dealing with the matter up front and letting the issue burn itself out is the best long term approach to keeping your own sanity.
There's a technique to the second one for making sure your bases are covered professionally since you're in potentially risky territory. Part of it is reporting what's happening to your manager and HR (paper trail). The second part is saying something like "Look, I'm not interested in you, never was. You're not even my friend. You're my co-worker, and we're going to hang out with co-workers. Are you okay with that?"
In my experience, you have two real options:
1. Add no new information
2. Add new information as unambiguously as possible
I've personally found that dealing with the matter up front and letting the issue burn itself out is the best long term approach to keeping your own sanity.
There's a technique to the second one for making sure your bases are covered professionally since you're in potentially risky territory. Part of it is reporting what's happening to your manager and HR (paper trail). The second part is saying something like "Look, I'm not interested in you, never was. You're not even my friend. You're my co-worker, and we're going to hang out with co-workers. Are you okay with that?"