Brianna is a minor character from Pokémon: Battle Frontier.
In Harley Rides Again, she went to the Wisteria Town Contest to speak to May but decided to just send her a letter when May lost. However, she forgot to sign it and, as the letter came with a rose, May mistakenly thought that the letter was from Drew. May kept the letter until she met Brianna shortly before another Contest in Spontaneous Combusken. It was there that she discovered what the letter actually meant.
Brianna reveals that when she wins the contest, she'll reveal her feelings to Drew.
Brianna does not let the subject drop and, after they both get through the appeals, Brianna asks May how she feels about Drew, causing May to blush and stutter that she hasn't thought about it much. After the Contest, Drew assures Brianna that she is a good Coordinator and she faints in May's arms.
Brianna reappeared in Thinning the Hoard!, where she was seen watching the Kanto Grand Festival from her home. Her home is shown to have various pictures of her, Drew, and May.