Amazy Dayzee is Rare and very difficult to defeat. Go to Flower fields and take the Lower right path on the east, walk trough the obstacles until you 'll see a field of flowers with Dayzees, go to the right for the other location and go back, she looks yellow and is glittering, when she stands there , fight and Defeat her to get a lot of Star Points.

Note: to see her again. let Mario sleep and look back, on this way you can repeat the trick.