She can take the GMAT whenever she wants and is ready for it. It's not somethig you have to "qualify" for. She will need to prepare for it, though...practice tests and studying test strategy (the GMAT is not like college tests so you need to learn about the test itself).
I would suggest she get some good prep books and plan on studying for 2-3 months. Official Guide (tons of practice questions, but no strategies), GMATPrep official practice tests (free at http://www.mba.com
), and Cracking the GMAT
book with DVD from Princeton Review
(great strategies and practice tests). You can get the OG and Cracking books from Amazon.
I would not suggest she go for an MBA right out of school. Great acads and GMAT scores are rarely sufficient to qualify one for immediate b-school enrollment. She won't get nearly as much out of it without real professional experience, and she'll have a harder time getting a decent job afterward. She should get at least a few years of experience first. There are a ton of well-qualified students from India applying to top American schools, and she'll need to stand out with solid work experience.