Sounds like you have some work ahead of you. Do you have a trainer lined up to help you out? If not I suggest you get one.
From what I understand she was put in a stall and not ridden or worked for 3 months and then was brought to you right? Thats a long time for a 3 year old to go without some reminder work. She may have been going good at the time, but young horses have short memory's. She may have to start over at page one in her lessons. Good luck with her, and stay safe.
"Until one has loved an animal, part of one's soul remains unawakened..."
- Anatole France