I believe it is your decision whether to have her spayed right now or not. If you think about it, getting her spayed now and aborting the kittens
is probably the best choice. I read the thread where you wanted to get all your ferals fixed. IF you let her keep the litter, and she has them outside, the kittens will become feral too and then you probably wont be able to find them homes, then theres more cats you will have to pay for to be fixed. IF you trapped her and she had the kittens inside, could you find enough homes for them? Would you be willing to keep any, if you couldnt find them all homes?
I remember you said that you get them spayed at the Humane Society, instead of at the vets cuz its cheaper. And in one thread i think you said you couldnt afford a vets appt. ATM? Could you take them to the humane society instead of the vets, for check-ups and what not? Just a suggestion bc I take my cats to the Humane Society for shots and check-ups and all, since it IS cheaper than going to a private vet.