Considering your sister's 90.4 percentile score in the SC+Female category, it's likely she's cleared the JEE Main cutoff. Given her accident and subsequent recovery, it's impressive that she's been scoring above 50% in JEE Advanced mocks.

Since she's already performed well in JEE Main, it's advisable to focus on JEE Advanced preparation. With her existing preparation and mock test scores, she has a good foundation to build upon.

To better understand the transition, note that JEE Advanced has a more comprehensive syllabus, including topics like Thermal Physics and Electrochemistry, which aren't part of JEE Main. The question format and difficulty level also vary between the two exams.

To maximize her chances, your sister should:

- Review and refine her concepts: Focus on strengthening her grasp of key topics, especially those unique to JEE Advanced.

- Practice with mock tests and previous year papers: Regular practice will help her adapt to the exam format, timing, and question types.

- Manage her time effectively: Balance preparation with rest and recovery to avoid burnout.

Remind your sister that her hard work and determination have brought her this far. Encourage her to stay positive, focused, and committed to her goals.