We had a BSL hen from our breeding that did more than dip a toe in the rooster pool. She laid eggs for a little while, then her production died off. The rooster that was with them was aggressive towards my wife, so he went into the pot. This little BSL hen then started to get a larger comb and grew out her wattles...then started to crow. Shortly thereafter she started taking on all the rooster roles, including breeding. When I slaughtered roos recently, she was on the list.
When I opened her up, her ovary was dead as was the whole egg laying tract. She had an oddly shaped teste on the opposite side. She had some other funky things going on internally (some of her organs just didn't look right compared to other healthy birds I've slaughtered), so we didn't save her meat. We didn't try incubating any eggs from the hens to prove fertility, but she was doing everything a roo was supposed to do without any of the nasty attitude (which we expect from all of the males that were out of her sire).
I'm not saying yours will be doing the same, but if you notice her egg production stop, then be prepared for full on "Roo mode."