Nesam isn’t able to undo Solttam’s trap, but that doesn’t necessarily mean that her abilities are weaker. A suyori/Elyeo can sort of ‘tame’ the plants and fungi around her, molding them to her specific style of control over time. Solttam lives here, and Nesam does not. This gives Solttam a distinct advantage.
There is even a saying among the people of Keol: ‘to fight a suyori in her own garden.’ It means something like fighting an uphill battle.