Did she know that where her wings are?
Definitely not. When her wings got removed, she wasn't aware of it because of the liquid she drank. She found out next morning. After much time has passed, she never mentioned that she knew where her wings were. She doesn't have far-sight or a fortune ball to know where is her wings are, or whether they are still unaffected.
Why doesn't she grow her wings?
Because she can't. She made Diaval as a shape-shifter and called him her wings. She needs her wings, but she can't grow them back. That's why she made Diaval as a raven shape-shifter.
Why didn't she try to get back her wings?
Through her actions, it's clear that she wants only revenge. She hasn't given a thought to getting back her wings and she might not even know if they are still there. And direct fight with Stefan is risky because he knows her weakness.
But she can do that....she can do that but why not bring back her wings?