How old is she? It can literally take a couple of seconds for a successful mating to take place. If I were you I would get her booked in for a spay tomorrow; that way if she has been 'caught' it is still far too early for her for there to be any actual kits and for her to know that anything is there: rabbits are induced ovulators so the act of humping will cause her to ovulate. Tomorrow she may not be pregnant but a few days later she might well be. I wouldn't wait until there are actual kits that can be palpated when you know what has happened today. Please, please don't ever let unneutered rabbits 'play' together even supervised as it really does only take a second...
I remember it happened on here a few years ago, someone thought they'd just see how the buns got on; the male hopped on, the owner took him off straight away, 4 weeks later, kits arrived.