Never a good idea to mess around with employees. Can’t go back in time and change that but the best thing to do moving forward, IMO, is to stop engaging with her in any flirty way. If she has dropped off interest let it be. Really, this isn’t some social group dating scenario where you are at leisure to ponder over her actions. She’s your employee, your are her employer and the risk is way way too high for you, not for her, remember that. It’s not appropriate, and you are risking your job your reputation if you don’t let it go. That’s really all there is to it here. I don’t advocate cheating but if you want some strange, keep it away from the employee pool at least.