Ikr, make it feel like the story doesn't make sense. Like all of a suddenly the mother want to poison the fake son when she was supposed to used her.
Yeah and they're fifteen. They haven't even reached her height in heels yet and she somehow thinks everyone is going to suspect the elder is a girl enough to poison her? SHE knows her daughters are nearly done growing and at their adult height but girls mature before boys so she can buy a few more years by telling everyone he is just a late bloomer. Poisoning the elder before the younger is even married is a fool's move because the wedding itself takes time and then, you have to have an expectation of more than nine months before labor and delivery.
Is this really the same woman who killed anyone at the birth of twins who wouldn't comply to her gag order (because it was more than just the nanny and the doctor in there) and took control over a family in such a succession mud slam they needed her to have a son to shut them up? We see her after she is fully in her power but crap like that takes cunning and foresight. We aren't going to have as good of a payback payoff when she is taken out of the picture.
A lot happened in such a short time