Margarita is also a Russian name, though very uncommon. My name is Margarita, but I have never come across any Russian women with this name under the age of fifty. I guess it used to be more popular in the past. The three standard Russian nicknames for Margarita are Rita (Ree-ta), Margosha and Margo.
One comment mentioned that Margarita is rare in Russia. It's somewhat true, it was a common name for an older woman, but it has come back in style. In the school I worked in we had quite a few for the small size and most of them were in the younger classes and I've noticed them popping up more often. Eva, Elizaveta and Polina are as well.