Haha, I think that is Isabelles lifelong inspirational quote. "I didn't fail to place the PWP, I just told you 10,000 places you can't have it."
I'm not entirely sure on the workings of getting her down the cliff. I think you need to wedge her onto one of the diagonal bits of cliff with holes and then run at her and trip, or something along those lines. I tried finding the video I saw before but no luck yet. But if she does allow you to place pwp once you get her to these places I've figured out how to get her to place them in the ocean, but only if you have a sideways facing lower waterfall. xD You have to glitch her into the water at the bottom of the waterfall, and then place a pwp that overlaps into the ocean, which might be impossible with a south facing waterfall as she places them a square above where you are standing.