I say we go for the waterfall. Our previous attempt at talking with Yamame was less than successful, to say the least. Like you said, she probably hasn't had a change of heart, and she's pretty good with those tethers. Not to say it would happen, but stopping to engage her now may end up with Nazrin all tied up, drowning at the bottom of the river. On the other hand, if we go for the waterfall, we have a chance of escape so we can get help.
So, I say we just keep going for now, and only engage if we think we won't make it to the waterfall without being attacked.
(Oh yeah, I've been watching this thing since near the beginning, but I've decided not to post in these things yet because I have trouble making actions that are actually helpful and accomplish something. That, and staying in character with other people's characters, namely ZUN's. So yeah. Just watching for now and giving out my ideas.)