How did Maleficent obtain the princess' hearts?

[Xera Highwind]

In Birth By Sleep Maleficent begins her search for the Princesses of Heart when Terra releases Aurora's. She then mentions that the keyblade is nessessary for obtaining the Hearts of pure light. She then has almost all of them when KH1 starts. How did she achieve this? There was no one with the power of the keyblade in between the games.

 

[Chuman]

the artificial keyblade of hearts that ASoD invented and had riku use.

 

[Antifa Lockhart]

the artificial keyblade of hearts that ASoD invented and had riku use.

That's nonsensical, that Keyblade was made OF those same captive hearts.

At the time, Maleficent needed the hearts, but without a keyblader, she probably made do with just having the princesses gathered in general and once they were together, the Keyblade of Hearts was conjured by their presence. We see Maleficent create the way with her incantation, so that's as clear an answer as you're going to get.