Which e-reader or tablet is best for a twelve year old?

This is a birthday present for a 12 y/o who worked really hard to improve in school last year. I want to get her a special present (in august), and I think she would like this. Unfortunately, I am not very tech-literate, so I need direction. She loves to read, so I thought e-reader, but she recently got a facebook now, so I think it would make her feel "cool" to be able to check that on her new device, and maybe surf the web, but it has not been easy to locate many e-readers with color screens, so then I thought tablet. 3G would be useful, as we travel a lot, but I guess not mandatory. I don't think she is responsible enough for something as expensive as an iPad. Would like to keep it under $300 ish, so I won't be too upset if she breaks it. Also, I would prefer to not be restricted to buying ebooks from one exclusive place if that's possible. Most important is that the device makes a good e-book reader, because she does love reading, and i want the gift to say "I know you well". I have been researching on bestbuy.com and amazon.com, but I am so confused by all the Android and E-ink lingo, etc. Suggestions?