Then what are you doing here? Also, I go faster than 20mph. So, I don't feel stuck riding on the road.

You may go faster than 20 mph, but 99% of others do not. However, even you riding at 20 mph is a conflict for someone wanting to legally go 30 or 45 mph. This is all made worse with drivers not knowing what bicycle riders will do, often compliments of a road system designed for cars and so bicycle riders have to do things a bit differently and different riders do things differently and while you may know what you'll always do, drivers do not.

Conflict, Fear, and Not Sharing | streets.mn

I don't think that it holds up, the inevitable conflict due to different speeds. With urban and suburban driving we have to constantly deal with slower vehicles - turning, merging, cutting us off, stopped, or just plain driving slow - and we handle it in the normal flow of traffic with the normal rules of traffic. The only things we have to do differently on bicycles are keeping right due to FRAP laws, and (sometimes) slower acceleration. Neither of these necessarily mean a disruption to the normal flow of traffic.

I suspect she is sweet on you.

Had an A-hole boss (ex-Green beret) that hated bicyclists.
Saw to it that I could no longer park my commuting bike inside the building. He ranted about me going to get killed on that 'stupid bicycle.'
Had the last laugh: he died ten years ago form a heart attack.

There is no way to properly defend the action of every cyclist. Your boss may just have been having a bad day and that was the only way to express herself. There is no need to argue, just let her vent her frustrations.