I think she got it because she fulfilled the criteria very well.
She broke record after record during the TD era, had her own movie, TV cameos, movie roles: personal achievements
She donates money from her music to charity and helps UNICEF in Madagascar: Philanthropy
She has been in the business for five years, and achieved much more than many pop stars do in 15.
That said, it's still confusing why Gaga and Rihanna don't have one yet.
And not people underrating the impact of the Walk of Fame. 10 million visitors a year.
Also, the 30,000 is a one time fee.