Asked and answered - it's Tink. The Blue Fairy is part of the show, but comes later. Also already answered.
If you need "proof", consider that the tram spiel on the way in from the parking lot (which I realize lots of people probably never hear) includes the scheduled events for the evening. During that spiel, Wishes is described as "featuring the flight of Tinkerbell". (It's not a pre-recorded spiel, but they do say the same thing every time.)
I wouldn't go by the tram spiel since they also refer to MSEP as the Electrical Light Parade and in one instance called the castle Cinderella's Palace.