I believe having a NEET Score of 646 as well as AIR of 5800, and probably Tamil Nadu Home State Quota your cousin can easily get allotted Government or State Medical Institutes in Tamil Nadu. Tamil Nadu has excellent medical schools in almost every district. Another excellent Medical school is CMC  Vellore, though it is private but provides excellent medical education at a low cost and is also one of the Top Medical institutes in India.

As far as Chennai is concerned your cousin should target Madras Medical College, Government Kilpauk Medical College, PGIMSR, Stanley Medical College and many other Top Medical Colleges with Excellent Infrastructure, Faculty and Hospital Facilities. Do keep an eye on the Government and State Medical Counselling and Procedure. For more information and college prediction do follow the link below.

https://medicine.careers360.com/neet-college-predictor?icn=QnA&ici=qna_answer

Hi

You have not mentioned the category you belong to, so I am  assuming  you from general category

It's quite difficult to make  prediction as  cut off marks/rank for medical colleges depends upon various factors like  number of students that appeared in the exam, kind of marks obtained by them , toughness level of the examination etc.

But when we go through previous data then it suggests that with 646,    you hold  a  very good chance in  govt Medical College under Tamilnadu state quota

And yes,
You have high chance to get a seat in Government Medical College in Chennai

For example,
in neet  2019, 531 marks for general category got a seat in   Government Medical College, Omandurar Estate, Chennai under Tamil Nadu State quota

And you also have chances in following Government Medical College under Tamilnadu State quota

*ESIC Medical College, K.K. Nagar, Chennai

*Government K.A.P.V. Medical College, Trichy

And more

To get the complete list of colleges in which you have chances, you can go through our college predictor at

https://medicine.careers360.com/neet-college-predictor?icn=QnA&ici=qna_answer

It gives you a personalized report with top college in which you have chances for admission , with the help of predicted colleges you can make better choice while filling your choices of colleges during your counselling

Thankyou