When I have made quilts for someone, I have picked everything. They were thrilled to have a quilt hand made just for them! However, it is nice to have a color to start with. So, I would do one of two things:
1) Let her choose the focus fabric and you surprise her with the rest; or
2) Make the entire thing a surprise.
She is going to LOVE anything you make for her because you made it and you made it just for her.