Why couldn't the adoption thing done before the emperor married someone else?

i think it's because she didn't think she had to go to that extent because
spoilers


rose has memories of the past so she's shocked when patrizia became queen instead of petronilla. because if it were petronilla, rose could just repeat her actions in the past and easily become queen again. being adopted was basically her last resort/the ribbon wrap in her plan. but patrizia was able to thwart everything and so you can say rose was struggling and kept messing up

Ohh thanks