Hi sheetal,
After 12th, as you are from science stream ( if you have medical)  you get into neet then afmc and get into military medical services.
OR
You are eligible once you have completed your graduation .

When comes to Indian Army, there are various entries for women.

For technical branch (for B.Tech/B.E) - SSC tech (women ), SSC non tech (women), NCC special entry women (If you are an NCC cadet).

You can also appear for CDS which is a UPSC examination.

For other streams such as arts , science etc - CDS and NCC special entry .

For PG women, they can join AEC- Army Education Corps.

For law graduates, JAG entry.

These are the various gateways for entering the Prestigious OTA (Officers Training Academy, Chennai).

For IAF, you can appear for AFCAT exam in your final year.

And for Navy, UES in final year and other entries as per their notification.

You have to face the SSB interview to get recommended for the services.

I am sure that you will make it. All the very best.