Wow, we're hitting the levels of complaining that cannot be even possible.
This is adding flavour and depth to the character, giving the moment of doubt when she traveled so far, too far to be redeemed, and yet for some reason she sees in Anduin her old self. This is the reason she's hesistating, she's not going to make him, because he's not fighting, he's looking into her eyes and doing "make your decision (for me)". And this is what makes her shaking inside right now.
People screaming R E D E M P T I O N are funny now.
Sylvanas cannot be redeemed, but she could be not a plain villain, but a villain with some flavour and I love it.