If you haven't already, do remove the little deceased baby as the others have advised. But start handling the newborn now. Pick her up, cuddle her, blow gently on her, hold her against your chest so she can feel the vibrations of your heartbeat. Momma kitty might be a little alarmed at first, but speak to her in gentle, calming tones - she will get used to you handling her baby. Don't let Momma get stressed about it though, if she postures or otherwise gets horribly upset, put the baby back down close to Momma - she will sniff and then begin to lick your scent off the baby. But go back a little while later and handle baby again. Keep this up until Momma knows you aren't going to harm her and permits you to hold the baby without getting upset.