You might consider trying again when the weather cools off a bit. I have a few does that refuse to breed when it's too warm. They may think it's just too hot to raise a litter.
We have had brutally warm temps in the Northeast, she may just be more willing if it cools off a little. I'd give her another chance. I have several Mini Rex that are funny like that, but once the weather cools down, they are more than willing.
I'll retire a doe when she doesn't conceive in 4-5 tries. Or when she doesn't "bounce back" after a litter, or when her litters start getting smaller and smaller. As Roger said, I have does that are 4 and 5 years old and love to have babies. I've had does that turned 3 years and refused to ever have another litter...
As far as spaying the rabbit at that age, a good vet would be better able to assess her condition and health. Yes, it's possible to do it safely. (Bucks are always easier than the does.)