Is she a feral cat? Or abandoned, and nervous being in? I agree that being in labor for so long may kill the remaining unborn kittens. She could have a breach kitten stuck in the birth canal, and she's unable to push it out. A shot of pitocin at the vets will stimulate contractions again. It could be she's very worn out already, and may need medical intervention. If she's aggressive to people, a large cotton laundry bag with a cinch cord works terrific for containing, and calming a cat. Just be sure to put it in a carrier for extra safety. The bonus is, the vet can examine her in the bag without having to drag her out. Hope things work out OK with the mom to be...keep us posted please!