Hi ya,
I have just read your plea,
I would be very surprised if she is in season, it is probably her hormones running wild & a scent that she is giving off at the moment that he likes!
I would keep them apart just incase he slips a quick one in and in another few weeks you will have another surprise on your hands as well as a very tired/poorly bitch.
Better to be safe than sorry as I say.
Love Carla.x