plus..im quite sure there was plenty of flirting prior between the 2...the story as told makes no sense.
If she so easily complied with his request to unbutton her shirt, that tells me she wasn’t surprised and must have given him the idea that this was consensual. I’m a woman and during my career a lot of guys I worked with and for came on to me, but if I let them know I wasn’t interested that was the end of it. Lots of consensual affairs go on in offices, but rarely outright assault.