copying backup from Iphone 5on my iMac to new Mac air

My wife used to sync her I phone and her iPad on my Imac.

Now my wife has her own Mac air and want to copy her backups on my iMac to her mac air. Is that possible. Because if she wants to sync on her mac air she will loos the data what is on her phone.

I read that it can only be done the other way around.

Some time ago you could do by merging

Can somebody help me in this

Hans