Graendal being the only one capable of this seems unlikely. For one, we know that Ishamael controlled Hawkwings through compulsion, and his mind was still intact enough to conquer most of the known world so the compulsion would have had to be subtle. Verin was also able to basically invent a weave like this from scratch.

Graendal was the greatest in her field in the entire world. That however does not mean that she was the only one who could do such things. It just means that the others are a bit less skilled. That however does not automatically translate to the idea that subtle compulsion is impossible to all the other forsaken. Heck, the fact that Ishy could do it already proves that she was not alone.