For really little girls I think you’re better off with having a small posy (very little bouquet) or a pomander (a small-ish sized ball of flowers) with a ribbon handle instead of a basket where she drops petals down the aisle. You can also choose one bloom for her to carry instead of several.
If you’re not insistent on her carrying something floral have her carry a “magic wand” -- a stick covered with ribbons that she waves down the aisle -- or you can have her blow bubbles.
Is she your only child attendant? Have her be your ring bearer and carry your “bands” on a ring pillow.
Think about your wedding’s location and theme and see if there’s something you or your florist can create that coordinates well.