Thanks everyone. I think I'm really going for the route people suggested: "your criticism is appreciated but not asked for. If I need something I'll ask Sensei" This really does 2 things: I speak my mind while being polite, and remind her of her place while not directly burning her ego.
Is she usually correct?
No. A lot of the time she was telling me to do X Y Z, then Sensei came to the rescue and told me to do A B C. I thought that should remind her that she should not be giving me instructions, but as soon as Sensei leaves my ears get harassed again. It's amusing and frustrating at the same time.
Usually I try to stay as far away from her as possible. But one day she was sitting next to me and was about to salute, I had to shut off my peripheral vision and go directly in the opposite direction to look for another partner. This is horrible etiquette but I had no choice. So I wanna put an end to this.
I'm a 3rd kyu and in our dojo, men wear a hakama at 2nd kyu and women at 3rd kyu. So evidently I'm really hesistant to "talk back" in respect to the "fancy dress".
Frankly I think Aikido is a lifelong lesson and everyone makes mistake from 7th kyu to 4th dan. Our goals should be to help each other train, make mistake and improve together, not to harass.
Now I just wonder, have you encountered something like this personally?