If she isn't fixed yet, don't even think about it! You'll end up with a litter, that might be the reason she wants to get out so badly now. Once she is spayed, her urges to escape should decrease.

My cats used to be indoor/outdoor. I lost two cats to cars (way out in the country - on a private road! So even minimal traffic can have a deadly effect) and one just vanished. It is totally heartbreaking, so I said never again. Mine stay inside now, and seem happy. Hanna bolts for the door once in a while, but I don't think she'd ever really go out. There are so many things besides cars that are dangerous for cats - people , disease, traps, fights, fleas and parasites...the list goes on. Plus domestic cats can do a number on songbird populations, leading to more people discriminating against cats.

I'd spay her, that should calm her down.