Check the pinned post on CSPA at the top of the thread:
http://www.visajourney.com/forums/index.php?showtopic=110679It has a calculator that will help you understand eligibility for CSPA. If application has not been approved, wait until it is approved to use the calculator, as otherwise, there are just too many unknowns. However, once you have an approval date, if priority date hasn't become current, you can enter different dates for priority date becoming current to understand when she will be 21. If you don't think the visa category is likely to move along at that pace for her to age out, start thinking of other routes she can come to US (e.g., marriage, student, work, etc.)
Hope this helps.
Regards,
Sanjiv Patel