A certified waffler is someone who waffles so much that they could practically have a degree in it.
Waffling is just basically someone who is just constantly yapping about random shit thats irrelevant.
Girl: Tells a long pointless and irrelevant story : "...So that is why I didnt reply to any of your texts for the past week!"
Guy: "Naaahhh ur just waffling now... certified waffler!"