I don't buy the rig knots either, but smaller hands on the right size rope...not that her rope differed in size than theirs, but the overall size of the rope could have been better suited for small hands to remove knots in them. My first impression, when I saw the challenge, was thinking it favored Abi. The overall difficulty was neither rigorous, or stamina oriented, although it was strenuous. Not just untying the rope was to the advantage of smaller hands, but also climbing thru what was like a part of a play structure for kids... Size advantage again to Abi. Rigged? More like some luck, some weakening of a challenge to make it easier for someone like Abi or any smaller weaker player to compete, meaning dumbing down the challenge isn't necessarily rigging it, and her determination, which is where she does deserve credit, all formed a perfect storm.
Having said all that I care less for her and wish she was gone before the season started. I could be more brutal and vulgar, but I'll refrain.