I think people forget that Semirhage was a shielded channeler. Without the Power, the Forsaken are less than normal people. They rely on their incredible skills and powers with saidin or saidar to create their legend. If you manage to take that from them, they are useless.

Semirhage had only been a captive for a few days, so I'm sure she was thinking of something. However, she was essentially at their mercy once she'd been captive, as surely as Moghedien was. Both of them relied and needed one of their peers to rescue them, and both were eventually helped.

Unfortunately the story didn't go exactly like Semirhage wanted - she expected torture and pain, but was only given humiliation and cheap interrogation, that eventually broke her. Later however, I think she fully lived up to her legend as the Lady of Pain. Rand was completely broken by her skills. She was by far more sadistic than any of the Chosen have ever been, and she even did it with saidin and physical force - imagine if she'd used her natural abilities.