Any real russian dating sites
Perhaps their introduction or 'About-Us' pages or other relevant pages could give you some background information of this specific Dating Agency, which could give you a 'good' or perhaps 'wrong' feeling about this site and their services.Also try to find out if they are a member of the Anti Scam Program.
Being prepared is being halfway your success in finding you Russian lady.
One of my favorite quoted expression is: "By failing to prepare, you are preparing to fail." (Benjamin Franklin - 1706-1790) But there are also many variants, that are 'close' to swindle practices, but not (yet) labeled as real illegal organizations.
These are organizations that will use methods to keep you as long as possible as a paid customer, or those who ask far too much money for their services.
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.