In the episode "Pokemon Contest! Lilycove Tournament!",
May and Kanata have a Contest battle, May using Combusken and Kanata using a Grumpig. Grumpig had a big advantage type-wise against Combusken. As the full time buzzer goes, Combusken has a fuller bar than Grumpig.
May wins the Lilycove Pokemon Contest ribbon!!
She now has a total of 3 ribbons!!
Here's a picture of the ribbon: