Wow, I really started this over a year ago? I thought it was more like six months.
Anyway, another update (just updated the trumpet topic, thought of this one).
After a whole lot of research, I decided to go ahead and upgrade my Blackberry (I now have a Bold, liking it), give sozlet the old Blackberry Curve, and activate a new plan for her (Sprint Data-only, which she's eligible for since the main reason we're getting it is for the two of us to communicate). I just couldn't find anything better than unlimited data at $29.99/ month.
There are downsides, like she can't accept calls. But most everyone texts anyway and she can call out if she needs to (20 cents a minute).
We got a fancy case/ skin so the phone doesn't seem too "mommish," which I believe was her word.
As soon as she took possession she changed the wallpaper, font, everything, and made it hers.
She's very happy with it thus far. Hasn't used it a lot, will really kick in when school starts.
Thanks to all for your feedback/ ideas!