India Entry/ Exit for US Born kids

Hopefully I have a peculiar case, my daughter (1 year old) has Indian Visa until Oct-09-2018. She entered India on May using her Visa, we received her approved OCI after she went to India, so we didn't use OCI for her entry.
Now we have a scenario where we want to extend her stay in India. Do I need to apply for an extension? Or since she has a valid OCI, we dont need to extend visa.

I read lot of people ended up in issue while exiting India for illegal overstay. Is illegal overstay an issue for only tourist visa people or for all visa types..