I hope that you can find someone willing to take the mom to be in before she gives birth. I'd call any local rescue groups and see if they have someone willing to trap her before she gives birth. The chances of the kittens surviving outside until 6+ weeks is not good. Approximately 50% of kittens born outside die from preditors etc. before they reach six months old. Then as others have stated they survivors start reproducing at alarming rates! Also a queen will usually stake out 3-4 potential nest sites to give birth in, so if she senses danger she moves the litter to safety. That doesn't work well for some litters. Several years ago I came across the aftermath of a raccoon feeding frenzy. Needless to say it was heartbreaking to see. Please try to find a safe haven for her! If I were local I'd take her