Astrophysics save my exams

You can't really enrol yourself for an ‘Astrophysics' specific course after 12th directly.
I have not heard of any institute offering a degree in Astrophysics at an undergraduate level.

With Opt2 after B.E/B.Tech in CS & E can she go for M.Tech in Astrophysics giving GATE exam.
Reason behind asking this is that after B.E & B.Tech she might have lost her touch with Physics and for GATE/astrophysics she will have to comeback again with Physics.
Astrophysics is a very advance and adventures stream of physics.

After your 10th exam or when you are in 10th
There are many exams related to Astrophysics carried out by mainly by NASA and others in which you can participate and know your potential and may be selected.