Question
Why my avs's flowers buds wilt before blooming ?

Answer
Flower buds that wilt before blooming is usually caused because of dry air.  The plant needs more humidity.  African violets love humidity so if you can maybe put some rocks in a saucer then add water, this will put the humidity higher.  Or set dishes of water here and there around the room.

Or you could spray HOT water over the plant daily for awhile.  Cold water on leaves causes spots on leaves but HOT water gives them  good humidity.  

Nancy