A Clash of Kings, in a Sansa chapter fairly at the end, during the Battle of Blackwater. And Cersei is telling Sansa that all the women will most likely get raped if the castle falls, and then she says:
“Were it anyone else outside the gates, I might hope to beguile him. But this is Stannis Baratheon. I’d have a better chance of seducing his horse.”

So, yes, Cersei trying to seduce Stannis at ANY point would just be hilarious. She'd do her best, and he'd be all, "stop clutching me, woman!" ;) I just really can't write Cersei.