I would think that, if she left the country before getting a green card, she'll have a hard time coming back in UNLESS she (a) wants to, and/or (

got permission to travel already. If she is gone, then the departure would be tantamount to abandoning (!!!) the immigration process you started, and that would, as a consequence, mean that the "declaration of support" would be a nullity. Nevertheless, I would DEFINITELY pull the plug on the declaration of support by way of correspondence to that effect:
(i) you disavow the affidavit of support from its inception;
(ii) such that it is and always has been a nullity
Be sure to include on the correspondence: (i) name; (ii) country; (iii) A-Number; (iv) K-1 Visa Number; (v) her Russian passport number; (vi) case number from a Notice of Action; and (vii) any other identifying information.
Send it everywhere you ever had contact...where you submitted the application, all the places that touched it, including, but not limited to, sources of Notices of Action, where you did your interview (if you did one), National Benefits Center, and anyplace else.
Want her back, eh? I know what you're going through...after all that work, sacrifice, emotion, dedication, commitment, money...you're SURE you can make it work! I admire your courage and fortitude, but (NOTE: I AM TRYING TO BE POLITICALLY CORRECT HERE...), it's likely to be the case that the only time you'll hear from her is if and when she needs money. Emotion, love, feelings, compassion, will not likely be a factor, so be a bit suspicious of sweet-talk. If she really DOES love you and want the relationship, she'll stick by you and be around. If not, she tries to sweet talk you and it doesn't work and she leaves, consider yourself lucky that she didn't sink her claws deeper into you before doing the exact same thing when she's good and ready.
Chances of rehabilitation of a relationship like this, given the totality of the circumstances, seem to me to be very, very sllight. Good luck! Go see a lawyer immediately. Check your personal message, too.