I don't honestly remember a lot about it learning to be responsible for my glasses, but I started wearing glasses at that age, too (and still do to this day).
One thing my mom did was tell me that I had to wear them all the time, unless I was "resting" (napping, laying in my bed, or sleeping at night). She said that for the first couple of weeks, I spent a lot of time laying in my bed "resting" because I didn't want to wear them. She was adamant about it, though and didn't give in when I begged, which I think helped me over the long term.
She helped me get in the habit of always putting the glasses in the same spot every night, which helped me avoid losing them (though I'm sure I lost them sometimes!).
I think after a while, as I got older, I realized how much better I could with them on, so I just kept using them.
It would probably help to get her to pick out her own frames... but unless she is totally crazy in love with the frames, that won't keep her wearing them.
Good luck with this.