OK story is simple:

A is a colleague from another department but I know him well.
He told me of a story he only dares to tell me now after nearly 3.5 years it happened.

A is a 40+ year old male (3.5 years back was late 30s).
New junior joined his department under his supervision, let's call her B and she was early 20s when she joined.
When B joined in, B immediately clicked with A and they talked / chatted a lot whether on IG or Whatsapp.
At first A was supposed to evaluate B's performance in her first 3 years so he thought B was just trying to get in good shoes so she chatted with him.
B has a bf but she illustrated to A as "not a confirmed relationship" even though it has been going on for nearly 2 years (at the beginning).

But somehow B can tell anything to A without any judgement or prejudice. Like her own stuffs, her family stuffs, even her relationship, her goals, her dreams etc.

After they chatted continuously for nearly 2.5 years, suddenly she broke off with the bf saying she had to do it.

At that point A tried to ask her out and all that but to no avail. She said she feels comfortable with the way they both are and doesn't see a need to elevate this "relationship".
That was also when she just got out of a major depression where she needed to take sleeping pills to sleep.
But somehow after rejection, she still keeps finding A even when A has now already changed department to my department.

I wonder sometimes, why women do this. I know she not interested but why she keeps finding A still when she already rejected him?