As I am a girl studying in IIT Patna, I think I’m eligible to answer this question.
There are currently 17% or more girl students in every branch and the number keeps increasing every year.
IIT Patna has one of the best campuses in India. We have a well built infrastructure and world class facilities such as any other IIT but since it’s a second generation IIT, some things are still developing .
Regarding branch change, there is an option of branch change for every student in IIT Patna in their first year. 10% of the total number of students in a particular branch can enter from their previously assigned branches but you’re only eligible for a department change if you’re in the top 5% of your branch.
For example, if a CSE batch has 80 students, then 8 new students can enter CSE from all the other branches given that they were in the top 5% of their respective branches.
IIT Patna’s campus is situated 35kms from the Patna City, in Bihta and is very safe for everyone including girls, people have varied perceptions about Patna or Bihar but if you come to the campus, you’ll notice that it is one of the most peaceful and secure places with top-notch security. There are guards at all the gates and important blocks of the campus for 24 hours and students can roam around without any fear on campus even at night. There are all the required facilities such as banks, shops, a hospital, foodcourts, canteens, night canteens (the best part) and I will assure you that if you choose Patna, you will not regret your decision.