A dependent cannot have a dependent. You can claim your teenage daughter as your dependent, and you can claim her child as your dependent. You should explain the IRS rules to her, so she does not file incorrectly. If she files first -- erroneously-- you can still file your return on paper and mail it claiming both of them. Hopefully she will understand the rules--unless she is being stubborn about it, as teenagers are prone to be. If she files incorrectly, the IRS will eventually sort this out and she will face repayment of the refund and penalties.
IRS interview to help determine who can be claimed:
https://www.irs.gov/help/ita/who-can-i-claim-as-a-dependent
https://ttlc.intuit.com/questions/3113432-who-can-i-claim-as-my-dependent
**Disclaimer: Every effort has been made to offer the most correct information possible. The poster disclaims any legal responsibility for the accuracy of the information that is contained in this post.**
