See for NEET there are no age limit till now. So yeah! he/she can sit for the examination, but your colleague isn't eligible for the examination of NEET because he/she didn't have Biology as a subject in 10+2. Now if your colleague want's then he/she can apply for open schools and get the 10+2 done with Biology as a subject. But there are cases going in Supreme court regarding the credibility of the NIOS students in NEET. So the aspirant have to take some chances in order to switch the career.

To know more about the NEET Eligibility visit the link below:

https://medicine.careers360.com/articles/neet-eligibility-criteria

I hope this answer helps. All the very best for your future endeavors!