So sorry 2young2feelold. Sounds like you've done everything you could to keep her in your home. Maybe it's time for a skiilled nursing facility with trained people who can deal with this.
There are also locks for windows that slip on where the window slides. No keys required, just turn a "wing" screw to tighten. If the window slides to the side you could also try just putting a stick or dowl in the grove where the window slides. It stops the window from sliding, and is pretty cheap fix. I used both these techniques, when I was a single mom, who couldn't afford a security system for burglars, but it might work with someone, with dementia.