There's a few ways Y'shtola's blindness can get the better of her. But one of the things we do know about her is that she is incredibly suborn once she makes up her mind. I can see her ignoring her own problems until it majorly impacts her further down the line.

Thancred doesn't have that issue as much because he's already had to deal with it back in 2.0 when he got possessed by Lahabrea. He knows he has to pay attention to his limitations and not ignore how they impact him. Y'shtola's never had to learn that yet.