What should be my strategy to convert IIFT Delhi? I'm a non engineer girl.

Assuming that you passed the IIFT exam for this year, keep it straightforward. You have an advantage over other applicants that are applying as engineers because your profile is unique. Also, a non-engineering candidate gets a 5-point entra over the engineering candidates and also 2 points for gender diversity in the final selection process. You just need to take advantage of that. 

Be knowledgeable about your graduation accomplishments and how you may use them for your MBA. You should also consider how an MBA can improve your skill set and enhance your professional career. If you effectively prepare your answers, you can easily make it through to IIFT Delhi in the first shortlist.

However, if you plan to take the IIFT the following year, there is no specific guidance for passing the exam other than practicing hard, being aware of your abilities, and doing what you can to minimize your weaknesses.