When should I separate my pregnant rabbit?

I have a Holland lop who I bred on Thanksgiving, so I am expecting her to have her litter around Christmas. I know you are suppose to separate the doe from the buck right after they have mated and keep her in a separate cage, but she does not stay in the cage with that buck. She stays in a hutch with another buck, who is neuter. The two are best buds, so I didn't want to separate them, because I know they may become lonely and depressed without the other for that long a period. Clearly I have to separate them before she has the kits, to prevent any stress or injury the kits and her could take. Should I do that now or a few days before she is expected to deliver? She has shown no signs of aggression towards Pumpkin (the neuter buck) and they are just as loving to one another as always, but this is her first litter!