Could it be possible… from your niece’s point of view, she may be reluctant to delve into college research out of financial embarrassment? She probably has no expectation you’re paying for her tuition, but without guidance, she doesn’t know how on earth she can pay anything for it either. She knows nothing about how financial aid works. Even researching colleges is completely new to her (as it is to most 17-year-olds). So like a deer in the headlights, she freezes. Avoidance is her comfortable coping mechanism.
I would talk finances with her. Stress that you love her, she is part of your family now, and part of that is setting her up for a brighter future, and you are going to learn and explore the possibilities, and together make good things happen for her. Remind her that you’ll have her back.