How old is your Nanny? It could be several things that are causing this issue. While you love the nanny, your babies may not. You need to speak with them and find out what's going on. To many times we assume it's the child. What your nanny tells you is going on can be different then what's really going on.
First, you should not assume that your little girls are the bad ones here. If they are doing these things, it might be that they don't like the nanny for reason other then they don't respect her. Is she talking to them respectfully when disciplining them?
Don't get me wrong, I'm not accusing the nanny of anything, but you must make sure your babies aren't being treated differently then what your nanny is telling you.
Kids act out when they are being treated wrongly. Have you talked to the kids and asked them how they feel and why? How is she treating them when your not there?
Has your nanny worked for others? If so, did you get a reference from others to know how good she is?
These pictures she took only shows what they are doing? But the question is why are they doing it? Your babies are more important then the nanny, you can't worry about hurting her feelings, if this isn't working out, then you need to find someone that can control the situation if it is a matter of discipline.
If it's a matter of how she is treating them, you need to consider that it's not just the babies fault here. To many children have been abused by babysitters, it's our responsibility to make sure they are in safe hands.
Even if it's just a matter of her not knowing how to discipline the babies, then you need a new nanny. If they are being treated wrongly, then you need to find this out.
Rev. G. Hudson