It's absolutely NOT what Cersi is doing. She showed up to help, at the risk of her own life, even before Jon agreed to bend the knee. Dany unlike Cersi actually does give a dam about the greater good, and unlike Cersi was willing to put aside her own agenda for the sake of it.
THat's why one is in Winterfell, while the other is at Kings Landing. If Dany was like Cersi, she'd be on the Iron throne as we speak and Cersi would be in the inside of a pine box.