That's a tough one!!
One way to approach it would be to start with the language that you would consider to be her first language, and that looks like either Russian or Spanish in your case, since that's the language she is spoken to, and which she will first learn to speak.
Or you could look at it this way - if you were to put her to a nursery or kindergarten, what would be the primary language of that institution?
Either way, it's a tough choice, and the availability of content might also play a role in the decision!