Astronomer

An astronaut is a person trained by a human space flight program to command, pilot, or serve as a crew member of a spacecraft. Although generally reserved for professional space travellers, the terms are sometimes applied to anyone who travels into space, including scientists also. Following are the general eligibility criteria to become astronaut:
(a)Bachelor's degree from a recognised university in engineering, Science, or mathematics etc. An advanced degree is desirable.
(b)At least 1,000 hours pilot-in-command time in jet aircraft. Flight test experience is highly desirable.
(c)Medically fit
India's first two astronauts were from Indian Air Force Fighter Pilot branch remaining Indian origin astronauts like Mis Kalpana Chawala and Sunita Williams were from NASA. Your friend can choose the path she wants to take because IAF has now open fighter flying branch to girls also. She can also go to USA and seek job in NASA after gaining additional qualifications and learning flying.

Physical cosmology is a branch of physics and astrophysics that deals with the study of the physical origins and evolution of the universe. It also includes the study of the nature of the universe on a large scale.
I think the most important thing one needs in a profession like astronomy and cosmology is curiosity. The conventional way is to go for Bachelors in physics, followed by a Masters and a PhD in physics. But some people are doing PhD after a Bachelors in engineering. One needs very good understanding of physics and maths as a prerequisite. Meanwhile, many leading research institutes like IUCAA, Pune organise short term Schools in astrophysics for school students, which should be used to get a deeper glimpse.