Considering the context of well, her being a doctor, it could just mean that she has a patient in need of her care lying in a bed...
Sure if a patient is waiting it would be bad but why specify that the man is nice? It does nothing except make the phrase "nice man waiting for me in bed" heavily implicative of something else, which is exactly what she wanted to get the spy to confront her.
The whole logic about making sure the spy tries harder to survive makes no sense. If there's someone else, then if the spy dies the doctor won't be alone, no big deal. Wouldn't it be more convincing if there wasn't anyone else? If the spy dies then the doctor would be devastated with nobody to fall back on. The spy has way more incentive to survive and return in this case.
IMO it's a ploy by the doctor to force more affection out of the spy. By implying or actually having someone else, the spy has to show more effort to not lose to the other party, thus instead of going of on the mission the spy spends more time with her. It's heavily manipulative and while I'd like more spy stories, this one just rubs me the wrong way.
As a last thought, if the doctor is just making sure to have a backup relationship in case the spy dies then the spy should find a backup herself in case the doctor leaves her.