Well, ignoring that some of that being unrealistic even for their wealth, especially for what she'd gain, I'd largely agree.I've spent little time imagining solutions to this and i'm honestly kind of unimpressed with Tsubasa's supposed intelligence if this wasn't all obvious as fuck to her... so i guess i'll just have to chalk it up to Selly being hyperfocused on where he's going with this story no matter how many obvious and simple solutions have to be ignored to get there.
You can SAY a character is as smart as you like, you can have them rattle off the most difficult questions you can google, or step in and say all according to plan at the end, but in practice an author can never really make a character more intelligent than themselves.
This generally isn't a big deal as long as you don't put their inner workings on full display, and that's the true crux of the problem here. We're being allowed to see a bit too much of the wizard behind the curtain regarding Tsubasa's machinations, letting us also see the holes and convolution in it.