This why Serena is my fav. anime character evah! And do not be confused at the ending. The reason why Eureka/Bonnie called Serena Satoshi/Ash is because Serena's wearing his clothes. P.S The reason she blush because Serena has a crush on him...
Clip from: Pokemon XY & Z episode 22 (https://www.youtube.com/watch?v=LzSF2L47Dz0)