I can see both sides of this.
Before I was pregnant with DS I felt the cold very badly, since I've had him I suffer from being too hot.
It was awful being cold, and layers only helped with arms and torso. Hands, face, legs and feet were still cold and painful and you can't wear hats and gloves in the office. But now it's awful being too hot, especially when you've stripped off as much as is decent already.
Is she cold or is she draughty? Because it does make a difference, although I know that sounds weird.
Layers do help with being cold but if she's doing something where she needs to move about and feel comfortable doing so, they can get in her way. And as I said, her hands and feet etc might still be cold even if she does put a cardigan on.
And if it's the draught blowing on her that's annoying her rather than how warm or cold that draught is, layers won't help because it's a different kind of uncomfortable annoyance.
But from your side, you can't exactly take much off to help you cool down, so the window or a fan is really your only option.
Could you have a fan pointed at you but not her? Could you shuffle the desks a bit so she's further away from the window?
And if it is the draught rather than the actual temperature in the room, could you change the air con setting so it's the room that's cool but without the breeze blowing on her?