Government & Defence Entrance Exam

You must graduate. Graduation is a must. Here are few things you can do, and DO adjust or modify them as per your own convenience :)
During your graduation years, revisit NCERTs and read all class 6-12 NCERTs (Social Science, History, Geography, Science) and develop an understanding of basics. ( For class 11-12 NCERTs, read selectively, I might answer how selectively in another answer)
Develop the habbit ofNewspaper Reading. Start by any simple newspaper, The Indian Express for example. No notes making. Remember you're just developing the habbit of reading. And during newspaper reading sit with a mobile with google search and google whatever news, its context, terminology, etc. You don't understand, as much as you can, but till a limit because graduation ki padhai bhi hai. When you get comfortable switch to The Hindu. Daily listen to AIR news, 15 min in morning (8.00 am for Hindi, 8.15 am for English ; and 15 min in night (9.00 pm for Hindi, 9.15 for English I think) the easiest way to revise major current affairs. If you have access to TV then news at 9 on DD news is also good. Develop an inqusitive mind. That's it. Developing basics by NCERTs
and understanding your surroundings and whats going on in your society, you country, your world, through current affairs. That'll be a LOT to achieve if you can in your graduation years.

Unfortunately, girls are not eligible to join NDA, in-spite of we woman getting in every stream and proving our-self, this discrimination is bad, but unfortunately we have to abide it. You cannot be appearing for NDA as girls are not allowed to get into defence after class 12th. However, the good part is that one can continue their dream to be a part of defense after graduation through various entries, which are as follows:
You can join OTA as an officer through CDSE entry. You can join IAF flying branch through SSC and AFCAT. You can be a ground officer in IAF through CET. If you do your graduation in engineering then you can have opportunity to move to technical field through EKT.