Ganj police station SHO Dinesh Kumar Jivnani said Nazia, along with her mother Rahima Yusuf, had gone to the Ramprasad Ghat at the lake.
She slipped into the lake and drowned, he said.
Her body was fished out and taken for post-mortem examination.
"We are waiting for the family members to reach Ajmer. A case has been has been registered.