What kind of Bible?

I would take her with me and let her look over the different versions and see what sits best with her. At 15 she should have some idea of what does and does not work for her.

Start here http://www.biblegateway.com/ and look up a passage, any passage. Scroll through the various English interpretations until you find one you feel is easier for her to understand and comprehend. Once you find a text you like use Google and search it with "Teen Bible". Such as NIV for Teens or NIV Teen Bible.

It's been said in the past that the KJV was written simply enough that a 3rd grader could comprehend it. It should be noted though that much of the debate around the KJV supposedly being hard to read is likely the result of those readers not being lead by the Holy Spirit.

A much larger issue for consideration is the conflict between "older" and "newer" bible versions. ( http://www.baptistpillar.com/article_686b.html ) If you compare verses between newer versions and the original KJV, you begin to see both subtle and major changes in the meanings of those verses throughout the entire Bible. It is up to you of course to decide what fits you and your dd best. Personally with some prayer for guidance from the Holy Spirit, she should never have a problem understanding and enjoying the KJV. Our 4yo and 6yo both do!

Personally I like the NKJV, I'm getting my 17 yo dd a new Bible and that's what I'm getting her. I used to think only the KJV was correct...that only that translation is accurate...but the Bible had been translated into that at some point too....you have to approach reading the Bible by asking the Holy Spirit to lead you, God will give you the meaning that you need, I don't think that only one translation is right. So I'd pick one that you think is easy for her to understand.

Mine is a Catholic Bible