If the top is still near you bax, I would be tempted to do something like stitch some velcro strips around the windows so that when it's parked for extended periods (as in overnight or while in school or work or whatever) and it's expected to snow, she can stick some soft towels over the windows.
This isn't going to protect from the cold obviously. It's just to keep her from having to scrape anything off the plastic to see. Especially the back window.
Also won't help the slush from collecting while she's driving, but at least it'll reduce the number of times she'll have to mess with them.
Scraping, cleaning and stuff like that are not plastic-friendly things.
Paul