We have a well-behaved kitty who loves to sit on the windowsill of our 7th story apartment. We try like crazy to get her to stop, but she loves it and foils any attempts we have to block her. So far, it's only been placing a heavy object in front of the window, such as a fan, but she is desperate to get out. She's a smart kitty, but a kitty after all, and she may leap towards a bird/bug and her death.
The other problem is the type of window we have, hinged on the side and extending inwards. This magical solution I am asking you all for would have to be removable, which is perfectly okay with us. I have added a picture.

Any suggestions would be appreciated.
Thanks, kiitos, tack!!
Ashley and Savu