Cain was already messed up from her childhood experiences, but the Cylons' attack and getting betrayed by her lover sent her off the deep end. She was aware that they could not take the Colonies from the Cylons and they probably wouldn't want those irradiated ****holes anyway. It was always about revenge for her, hence the reason she wanted to attack that comm relay/staging area at all costs. She didn't know about Anders and Starbuck's desire to rescue him. While there may have been some slight manipulation, Cain genuinely (believed she) shared Starbuck's views and admired the pilot's combat skills and creative thinking. EDIT: "Black Market" is the worst episode, but it is still very much watchable. The worst of BSG is still better than 90% of television out there.