Hen fighting my rooster?

I have 2 Silkies in my small backyard flock, they're about 18-19 wks old.
I know for sure that one of the 2 is a ROOSTER, it crows.

The other silkie doesn't crow, and it has never showed signs like other roosters, chasing hens.. and trying to mount them..etc etc..

Anyway, the Silkie rooster recently got sick and I had to remove him b/c the other Silkie started attacking him furiously .. and wouldn't stop.

So i took him out and gave injections of Tylan-50 for 5 days and kept him warm inside our garage quarantined away from any possible harm.

And he's now pretty much all better, but when I went to reunite him (with what I thought was his HEN) they started
attacking each other again.. and this time he fought back pretty hard.. and could've easily pummeled the other.

So, now I'm wondering, is this other one even a hen at all?

I've never heard her crow, but she's acting like a fighting rooster or something.
Crazy, I don't understand this.

Can anyone explain this, or tell me how to (FOR SURE) distinguish the differences between a hen and rooster in SILKIES?

She may also be a cockerel or just a dominant hen who does not want to relinquish control.