It’s hard to determine if it’s play or not on your rabbit’s part without seeing their interaction. As bam said, if he comes back out from behind the couch, he might not be scared, but then again, if he’s actually in a panic then he might just be running aimlessly.
Whatever the case may be, personally I would not allow this to go on. Rabbits and dogs or cats can be friends and hang out together but that doesn’t mean anything goes. I agree with bam, games like this can quickly turn serious if the instincts suddenly kick in. If the rabbit for whatever reason does get scared, he could give himself a heart attack before you even realized that he’s not playing anymore. You’re allowing them play out a “predator hunts prey” situation. I don’t think it’s a good idea, so many things could go wrong in a split second.
Our cat and rabbit are good friends and they spend time together every day, but we made sure the cat understands how she’s expected to behave around him. As long as she’s calm, they can hang out. If she gets antsy, bunny time is over.
Dogs are smart, I’m sure you could teach her to be calm around your bun in no time.
Clicker training helped us a lot.