>>36723915She could've just NOT thrown Twilight, who she had already managed to convicne she's the real Cadance despite putting absolutely no effort into a proper act or knowing anything about the relationship between Cadance and Twilight, into Cadance's cuckcave.
There. That's all she needed to do to win, and she still fucked it up enormously.
Chrysalis lost not because of bad writing, but because of her ego made her think she didn't actually need to put any effort into her plan despite that which came from her natural magical skills.