Actually, wild rabbits and domestic rabbits that are breeding constantly can still get cancer. As far as can be told, the reason that rabbits get cancer of the reproductive systems so easily is because they have so many hormones going on due to the fact that in the wild they are supposed to just breed like crazy, and they usually die before cancer can set in (most wild rabbits don't make it past 2 years old). So it is a good trade in the wild population, to keep the species alive. However, domestic rabbits usually live a lot longer, so cancer is a much bigger concern. It you have to spay her later, it will still be effective, as long as she is not older than 2 years. Very few rabbits get cancer quite that early, so if you can save up by around the time she is 1 year, 3 months (as you said you should be able to), you should be fine. Not a total guarantee, of course, but it is a lot better than letting her just go unspayed.
As for breeding, it's just best not to unless you have a breeding/show quality rabbit and are breeding to an equal or better quality male. There are plenty of pet rabbits already available, and the only time I recommend breeding is if the rabbit is good enough of a breed representative to produce babies that could compete well in the show world. If you do decide to breed her, definitely do your research and talk to people who have been breeding for a while.