I did not think 'juvenile' when I saw the quilt. I thought, "cute". Like many of you, I love bright colors too!
Does your aunt like bright colors? If it matches your aunt's personality it's perfect. Don't worry if it doesn't match her bedroom. Someone once said, "true art doesn't have to match your couch
". Especially if she's going through a hard time or something, pretty colors are up-lifting.
As an auntie, I will say receiving a quilt from you will be joyous, no matter what it looks like....