That's an interesting question. Based on my own experiences and the risk of uterine cancer in rabbits absent spaying, I would recommend you get both the mother and the daughter spayed. Bunny social dynamics can be quite interesting. There's no particular reason why the mother and a spayed kit shouldn't get along though at some point, as the female kit grows and becomes size-wise a threat to the Mother's dominance, they may have to resolve the issue of who is really dominant. I.e., they may go through a stage where they fight.
I have two spayed females who were littermates, Dorcas and Jemimah. They readily accepted the non-neutered buck that preceded them on my premises. At about one year of age, when the one we thought was the runt actually grew to be quite a bit larger than the other, the two had a very serious fight and needed to be separated again for a couple of weeks and then reintroduced. Having apparently resolved that issue, they have generally not revisited it -- at least, only revisiting it when additional bunnies and complex bunny social dynamics came into play: The male rabbit died and some years later, I picked up an unspayed female rescue rabbit, who fit in fine with the two littermates once she was spayed. Before that, she constantly picked battles for dominance with Dorcas. After spaying, as a threesome they got along great. They continued to get along great when we added our first Flemish Giant buck, Ben. Ben died an untimely death, and shortly thereafter we got our second Flemish Giant buck, Sam. For some reason, once Sam was introduced, Jemimah and Maddie really turned on Dorcas, who is the smallest of the rabbits. I have had to remove Dorcas from the general bunny population and keep her in a different portion of the house. Although I have tried several times to reintroduce her, her littermate Jemimah is always the first to launch an aggressive attack . . . Fortunately, Dorcas seems to enjoy being an "only" bunny.
There are certain things that you can do to discipline rabbits so that they get along better than they would otherwise as they go through the dominance-challenging phase. Rabbits are very social creatures. When one of ours has started to get aggressive with the others, we have generally given them a day or two of "time-out" by isolating them in the bathroom. A rabbit who is misbehaving and aggressively asserting her dominance will take this punishment very seriously. By taking away the possibility of social interaction, you have taken away the basis of her power, her sense of dominance.
Anyway, this is rather long. I ramble. I hope it was of some help to you in your weighing of the possibilities.
