You have two issues: Nursing and Sleeping. You should think of them as two seperate issues and treat them as such, so as to help your child start thinking of them as seperate activities too. When you decide to wean is up to you, but as long as you continue to put her in the familiar nursing positions and situations she will continue to demand what has always been given to her. If you continue to nurse her (although you will have a few sleepless nights), you should immediately stop nursing her in your bed or while lying with her. Find a new spot and new position and make that consistent. Or begin to wean her. (which is an entirely different subject) She is definitely old enough to wean from night nursing, and you can continue to nurse her in the day, which should keep her emotional needs fulfilled. But even in the day, avoid the night nursing places or positions.
So, on to sleeping, first you need to decide 100%, where you want her to sleep, b/c changing your mind and doing things differently one night to the next will make things a lot harder. Once you have picked your course of action, stick to it, confidently explaining to and encouraging yourself and your baby. If you are weaning to a crib, you should stop offering the alternative, sleeping in your bed, right away and consistently keep her away from your bed until she has transitioned. With my first baby I did this with a little bit of sadness, but once he was REALLY O.K. in his crib, we could go back to the family bed on occasion (mainly naps and early morning visits) and he could handle it, but weaning should be complete before offering the family bed again (which, is often just the most convenient thing). Once you have established the new sleeping situation, consistency, confidence, and calm are the key. If your child sees you calm, they will eventually calm down, too. They will also mirror the confidence. Your job is the consistency. Pick a new bedtime routine and start from there. If this means that you have to use the baby's room for a week or so, maybe the nanny will have to sleep somewhere else for a little while. You definitely shouldn't be trying to keep things quiet, because this transition will cause crying! No matter how gently you wean yourself away from her while leaving her in the crib, she will voice her feelings and wake the nanny! GOOD LUCK! Whatever you decide, follow your instinct...most likely, that is the best answer. YOU CAN DO IT and BABY CAN HANDLE IT!!