While on their way to Driftveil City, Ash and co. encounter a Gothita and its trainer, a young girl by the name of Katharine. It appears that this Gothita has taken a liking to Ash's Scraggy due to its staring and tell Katharine to have a Pokemon battle with Ash with Mandibuzz. If she wins, she'll have Scraggy for her Gothita. Will Ash agree to battle her for it?
Since Katharine's Gothita had feelings for Ash's Scraggy, Gothita must be female.
This is the second time Ash looked up Mandibuzz on the Pokedex. First was a wild one in BW045: Meowth's Scrafty Tactics! which it took Scrafty's den away because it did a bad thing to her friend without permission for the grub.
This is the second time Ash battled a Mandibuzz. First was Scraggy battling a wild one which it took Scrafty's den and wins with a newly learned Hi Jump Kick which Scrafty teaches him a new move, and now Ash's Tepig is battling Katharine's.