Using CMBs (remember) so Grom only has a CMD of 15. It's enough to qualify as an ankle grab. Letting it go into an uncontested pull seems a tad unfair tho. We will go for continued use of CMB. Still, Noshu is effectively giving up a chance to move up so she gets something besides a smelly ork foot in her grip.
Before it goes any further, Grom is required to make a Climb Check but since he has been way luckier than I have been, I am not going to roll it for him. 20+ will allow him to maintain his position without any penalty. 15+ means Grom does not lose any ground but he does lose his next action in maintaining his hold due to Noshu's interference. 10+ Means Grom loses another 'stage' of climb, loses his next action but does not fall. Below 10 and Grom's hold is too muddy and slippery and he falls off.