It seems like you've already made up your mind on not wanting to be a third (forth?) wheel in the relationship. If you are looking for something serious I would advise staying away from the woman because it doesn't sound like she's looking for one. If you are just looking for some fun, then why not since you connected with her sexually (However, be careful of STDs since she has multiple other partners). If you are looking for a serious relationship though I would venture a guess that she wouldn't be opposed from straying from y'alls relationship if the boss, or someone else who catches her fancy, comes along. She already said she would go back to her boss if the possibility arises, so that will always linger in the back of your mind. Just my two cents. I hope you work this out.