Hiya, welcome to RU. :wave:
I take it this is an accidental pregnancy? I would certainly recommend an emergency spay. Is the buck still in with her? If so you need to move him staright away, and book him in for his neuter. He can be rebonded with her 6 weeks after they've had their ops.
If you choose for her to have the kits, I'd really recommend bringing her inside (do it now, rather than waiting til she's had them). Obviously then they'll all need to be house rabbits until the late spring, as the temperature change would be too great otherwise. There's a chance they could survive in an outdoor hutch but, if it's another winter like last year's, not very likely. Tape snugglesafes under the nest area and make sure there's plenty of warm bedding. Cover the hutch in as many blankets/duvets/hutch covers as you can.
How big is the buck compared to her? if he's significantly larger then her kits will be too big to be born naturally, and she'll need a section. As her time nears you'll need to go and check her every couple of hours, more often if she's showing signs of being in labour (yes, during the night too!). If in any doubt, call the vet.
She'll need unlimited good quality hay (she should have this anyway) and start increasing her pellet/veg ration now in readiness.
Hope that helps, any more questions, feel free to ask!