I get that this is a potential integrity issue, provided that the girl in question knew the ex-bf wasn't single when he cheated, or continued to cheat with him after discovering the truth. In that case, a cool-headed, tactful consultation with the appropriate people is merited. I can also understand why OP may want to inform them about the past relationship, in case OP can't tolerate working with the other woman and needs to quit. What I don't understand is what would motivate the manager to undermine OP professionally. People can, and often do, separate private and professional lives. Unless we're missing a key point to the story, I'd think OP would have a harder time separating the two, and that she'd be the one more likely to engage in sabotage-as-revenge. In that case, as I said in an earlier comment, an earlier consultation might backfire, by the bosses giving the manager the BOTD in any conflicts. Maybe I just don't get it because I've (thankfully) never been in a cheater/cheated on situation, though.

The woman isn't necessarily going to have motivation to undermine the OP professionally. If she has an integrity issue, it's not going to be compartmentalized and restricted to just her personal life. It's going to show up in how she deals with people and situations in her professional life also. If she does have motivation to harm the OP's professional life, her lack of integrity will make the work situation intolerable in a short period of time. For that reason, I strongly suggest the OP take a pro-active approach and create documentation with HR before the interview/hiring is completed. The possibility of this move backfiring on the OP greatly depends on her current reputation with the bosses. If she's known to be a hard working, intelligent, thoughtful, team-player employee, her word on this matter is going to carry a lot of weight and will go a long way to protect her. In any event, it seems to me that the lesser of two evils would be to proactively create documentation versus coming to HR after the **** has already hit the fan. She doesn't (and shouldn't) be malicious about it, but just alert HR to the facts of the matter.

#85 -- People's personality and characteristics aren't restricted to just one part of their life. If the woman lacks integrity in her personal life, it would be the height of foolishness to believe this trait isn't going to show up in how she conducts herself professionally.

I'll be the first to say it; TL;DR