They are each 3 months old, the ideal age of pregnancy.
If it's 3 months like 12 weeks she's maybe not, if like 14 weeks it is more possible. Also depends on their personal development, some rabbits can stay like babies for longer and just act like babies. Maybe you're lucky then.
Watch them how they act have you ever noticed he grooms her extensively or humps, honks etc, maybe he is still not interested in her and they are just friends.
If she is pregnant then she can get aggressive when he tries mounting her it means she's not available she already carries babies. It is very hard to feel babies in her belly, you won't be able to notice probably until she gives birth. Rabbits are pregnant 31 days approximately she will start nesting a few days before that.
If you have plans on spaying her anyway I would suggest doing it right now as soon as you can get an appointment, in that case if she is pregnant already her uteruses will be removed with fetuses.
3 months is a bit too early to have babies, she is still growing herself and she would need to build new bones inside of her, she will take building materials from her own bones.
So if she is pregnant your vet might be able to find out using ultrasound or just go for a spaying surgery that would be easiest solution in your case.
Some vets would only take females for fixing after they are 4-4,5 months but if you can explain your situation it might be possible since that would be an emergency.
Anyway they should be separated immediately with min 1 inch gap between their gates.
she’s still a baby herself and hasn’t had a chance to grow to full size or mature to develop those motherly instincts. 
