Hi Yves,
Congrats to your wife for not allowing her disability to impede her from doing what she wants!
I just downloaded a free program called
Free Video Flip And Rotate from
Download Free Video Flip And Rotate
It worked very well in my test, and seems simple and intuitive to use. Load the original video file, select where the destination will be, then choose the rotation - 90 deg, 180, etc. Give it a shot.
If you like, PM me an email address and I can send you more detailed instructions with pictures and stuff.
Hope this helps.
-Chris