And even if Moiraine has balefire and Cadsuane doesn't (and regardless of what she knows, I would concede that she would never use it, effectively eliminating it from her repertoire), so what? One weave means squat. Given all the other lethal weaves either woman can use, balefire is pretty much overkill. More important than having the most powerful gun is knowing how and when to use it. Given Cadsuane's ter'angreal, she'd spot Moiraine well before the other woman could think where to weave.