Yep, same thing happened to me. She declared T67 and I'm toast. I was kinda asking for it by trading her copper, but figured it will get her to pleased faster and she always goes IW anyway for her UU. I also closed borders with her a few turns ago when she was going for a barb city in the SW-peninsula. Should have just let her get that I guess. Also with a different tech path (was beelining CoL more or less) I would have archery now and bowmen would be excellent here. Hinduism was spreading all over the place but didn't get lucky with a random spread.I think the problem was Celts went war mode. Needed to get them to pleased. It should of been a lot easier than I have made it. Taking down Celts has suddenly become a big resource drain.
I still think some peaceful opening is better here than going for catapult war...