China vs Russia, how to beat Catherine

[fcreativew]

The game is saved (I've been overriding so there's no way to go back in the past and make more changes) one turn before Catherine declare war on me. I've crushed the Mongolian empire (and all the others), except for one city, so physically I dominate most of the map, however.... Catherine it's way more advance in technology and she have possession of several atomic bombs she have no qualms in use over and over again.

I've tried pay my way into many city-states alliances so she have to face several neighbors but she have good enough units all technologically advanced to deal with them. I've tried to befriend her right before she declare war but she's hostile, she won't sign peace for at least 10 turns more than enough to pulverize my recently conquered cities and units. Besides me having more puppet cities, I'm more advance in culture yet not enough to win a cultural win since I've been focusing on domination. Game difficulty, normal.

I would greatly appreciate your input.