I’m not entirely sure of Cora’s motives here except that maybe she saw a lot of herself in Ana and also that Ana would do what Regina would not. Cora almost seemed as if she actually cared about Ana or at least dreamed of her success as if she were truly her daughter. Otherwise, why would Cora want to teach someone else to be like her?
I think it goes back to what Slurpeez just said: Cora and the Red King had an uneasy relationship.
Yes, the biggest motive was that Ana is VERY Cora like and Cora could control her unlike Regina, but Cora now has inroads to Ana’s kingdom that they are friends. She can control both kingdoms by ruling one and controlling the ruler of the other
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"He was a lot of things to me" "The only conclusion was love"