Take her to the doctor or dentist and have them say in front of her that she can't have it any more. Then do whatever else you can to comfort her at bedtime, but blame the doctor that she can't have the Nuk anymore.
This is what worked for me. I had been trying to wean my daughter off hers and it wasn't working. Then she got a really nasty throat infection that because she was still using that got pulled to the front of her mouth and her lips. Took her to the doctor, he said that, and we cut if off cold turkey. It was a few nights of crying, a few weeks of asking for it, and then a few months of the occasional melancholy about it not being around but then she was over it. Good luck to you!!