Paid more than Half but no considered dependent

I already filed my step daughter's return and said that she could be claimed as a dependent on our return.  Now I'm doing our return and it says she can't be claimed as a dependent.  She only worked part-time and was going to school part-time, but she made $13,210.  So is that why I can't claim her as a dependent?  Do I need to do an amended return for her?

 

Claudia H. Smith