How much percentile would be required in the CAT for admission at IIM Udaipur (PWD female) with 95% in X, 85% in XII, and 7.7 CGPA in a BTech?

One of my friends had a similar profile as yours and with just a percentile of 90.78 he was able to get calls from all major B Schools throughout India, even FMS. In fact you being a female can get in with an even lesser percentile. One need you need to keep in mind is that you will be giving your WAT and GD with General candidates so you need to prepare well in advance.

But you need to change your direction of thought for once. Getting an admission is easier than competing with talented peers and getting placed. Many times people from Reserved Category are unable to cope with academics and placements. So how do we tackle this issue? 

Since getting a high CAT percentile is easy, you should focus more on upgrading your profile before joining the college. You can work for firms in the following sectors Marketing/Consulting/Product Management/IT/Analytics/Finance. The panel interviews you on the basis of your grades, extracurriculars and work experience. So by working before joining you can increase your chances of getting admission. Target a specific profile and build your resume in that direction only. Lastly choose the college that suits your profile. For instance FMS specializes in Marketing whereas IIMC specializes in Finance.