The vet will be the best one to tell you how far along she is. The fact that her nipples are engorged and pink leads me to believe that she's pretty far along. Keep us posted. If you can, tell your friend to keep the cats separate (hers and the preggy one). It's much safter that way. The last thing you want to do is stress the mama out. She needs quiet, with no other cats going in and out of a room she's about to give birth in. It'll stress her out and could cause complications.