I still need to add the visa posts to the Russian travel thread.
I will provide details later, but here is the short answer: if you want to visit her home, you may face the stark choice between (A) paying for a hotel for the time of your stay, or (B) facing some possible unpleasant consequences, which could include inability to enter the Russian Federation in the future. If might want some day to make visits with her to her family, being barred from entry would be a sad state of affairs.
This wouldn't be an issue in most of Russia, but where she lives (norther Caucasus), the rules are different.
You can ask her to help you in two ways: first, she can look for anyone in Krasnodar who has had a recent home visit from a non-FSU foreigner. Maybe there is a (practical) solution to the riddle! (Be forewarned: one feasible method is bribery, but this can seriously backfire.) And if there is not, maybe she can find a real sh*thole of a hotel with a low room rate (you don't want to stay there, only get your paperwork processed).
One other possibility is to get "tricky" (if any Ukraine guys are reading this, they'll probably be saying "no way I'm ever goin' to Russia"): the paperwork issue is only triggered when you exceed a 72 hour stretch in one town, NOT including weekends. So for example, you could arrive to Krasnodar on a Wednesday afternoon, and stay at her house. The two of you could head to Black Sea resort the next Monday morning, stay at a hotel (and get your visa registered there) until Friday, and leave Russia on Wednesday morning. In this way, you could spend 10 nights at her home, without ever exceeding the "3 working days" limit in Krasnodar (but for God's sake, check my arithmetic). In such a plan, you would want to keep travel receipts or such to prove your movements to the border officials. As you can see, this takes military-style planning.
(Ingmar Bergman fans take note: dealing with Russian bureaucrats is not unlike playing chess with Death.)
Whatever you do, let's talk before you book your Russian trip ;)