It depends on how many months of Post 9/11 GI Bill benefits you gave her when you made your initial transfer request. Entitlement use is based on a 30-day month, so if she is going to school full-time, she would use one month of entitlement for each month in school. If she is on 4-month semesters, 3 semesters would calculate out to 12 months of entitlement use. I would recommend looking at her Certificate of Eligibility (CoE) to see how many months she originally had.
The only thing I can think of that could speed up her use of benefits is if she is taking an aviation program or a high-cost technology accelerated course. Those types of training use up benefits at a faster rate than other courses.
If you did not transfer all of your benefits to her, then go back in and make another transfer request. You can give any or all of your unused Post 9/11 GI Bill months of entitlement.
The other thing that could come into play is if you had used some of your Montgomery GI Bill entitlement and then switched over to the Post 9/11 GI Bill, you would have only received the same number of months you had left under the MGIB and not a full 36 months. So while you might have requested to transfer 36 months, the VA would have only transferred the number of unused months you had left. If her CoE shows she had 36 months, then I would contact the VA and ask why her use is accelerated.