These persons mostly don't answer your specific questions and don't give much personal information, but use general (predefined) text for their letters.This is at least a sign that you have to be careful.Only use real, professional and verifiable agencies.
Try to send copies of your original letters using postal mail or a fax machine at her office (if possible) and ask her if these letters are the same she received through the Dating Agency you are using.
I know examples that some Dating Agencies, with this kind of services, can create additional questions or add more text to your letters or even change your letters, just for the reason to keep you as long as possible as their customer.
You can also first visit our recommended agencies that you can find in this topic.
Write a detailed introduction letter (preferable translated in Russian), to receive a detailed reply of the woman If you write your Russian lady for the first (introduction letter) time, please write a detailed letter about yourself.
For the woman it's important to see that the man who is writing to her is serious about finding a new partner.