You're missing her actual play here. It was never a real complaint.
She "complains" to you about it.
You go "oh no you poor victim," but don't suggest you'll get involved. She gets one form of attention from you and another from him.
You say something foolish like, "I can see why." She gets validation from both of you and has a stronger case when she fishes the next party for attention.
You indicate you're going to resolve it. That would take away attention, so she pulls the "I actually like it."
3a) You let it be, she still gets attention from him.
3b) You take that to mean she'd appreciate "inappropriate" things from you as well and we reach #2 by a different path.
3c) You make a big fuss about it on her behalf, the male co-worker takes the consequence. She trades his long term attention for concentrated attention from others: the fallout from the drama.
Her reward is more attention (or maintaining the status quo) and all social risk is completely borne by the coworker and you. You picked the correct option for yourself, but she's playing a unlosable game.
You're missing her actual play here. It was never a real complaint.
She "complains" to you about it.
3a) You let it be, she still gets attention from him.
3b) You take that to mean she'd appreciate "inappropriate" things from you as well and we reach #2 by a different path.
3c) You make a big fuss about it on her behalf, the male co-worker takes the consequence. She trades his long term attention for concentrated attention from others: the fallout from the drama.
Her reward is more attention (or maintaining the status quo) and all social risk is completely borne by the coworker and you. You picked the correct option for yourself, but she's playing a unlosable game.