If the car is hers, then the registration V5 should be in her name and the Insurance should be in her name as well. She will in fact be the main driver, as even when she is teaching you, she needs to have control over the car. What for example would happen, if you drove 3 miles down the road and for whatever reason she needed to drive the car home. You are a provisional licence holder so cannot have sole control over the car. You need to have a full licence holder in the front passenger seat with you at all times, when you are on a public road. The idea being that if you got into difficulty they could coach you or take over control of the car themselves.
When you have passed your test and you become the regular main driver, she would then need to let her Insurers know this. Most Insurers will not allow you to Insure a car that you do not own. This is why they ask the questions about ownership of the car.