Rand refusing to kill <x> is irritating

In the shadow rising, Rand refused to harm Lanfear because she’s a woman - despite the fact she’s a forsaken. Yet in the Dragon reborn, he murders a female trader and all her party because he thinks they could be dark friends?

How does this make any sense? I know it’s a recurring motif that he doesn’t want to hurt women but he seems to pick and choose when this rule applies