Wise decision.
You're sparing yourself a LOT of grief.
It's up to you whether you want to try to show her that the Watchtower Society has done the very things she is criticizing churches for, but don't be surprised if it doesn't have any more impact on her than your points about the UN.
You might also say, "I've looked up the history of the Watchtower organization and based on that, there's no way I'm going to be convinced that it's God's organization."
If she wants details, you can give them to her. Put the burden on her to explain the failed Armageddon predictions of 1914, 1925, and 1975.
If you've read Ray Franz's Crisis of Conscience, you can tell her that unless she proves to you that he's lying about what he says about WT history, you couldn't possibly just the organization. If she says she doesn't respond to apostate literature, tell her she's free to ignore it but you won't.
That said, you're perfectly within your rights to simply tell her, "Thanks, but no thanks."