Embassy of the USA in Bishkek

B2 visa
I would like to invite my friend in Bishkek to visit with me in the U.S. on a B-2 visitor visa. I will be responsible for her expenses while she is staying with me and will also provide her round trip air fare. I will also drive her back to the airport to catch her return flight and will see her off at the gate. I intend to show her a wonderful time when she is here in U.S. and to take her to some of the more popular attractions in Central Florida like EPCOT and Uniersal Studios. She has told me I am supposed to send a letter of invitation. As this is my first time doing this, I am asking for your assistance in what to write and where to send it and how to send it. Do I write the letter to her? To the Embassy? To both? Do i send the letter by postal mail or can i send it by email? Is there anything specific that it should say? Do you need any documentation from me such as passport or just my address and phone number? Your assistance in this matter would be greatly appreciated. thank you..