I already did.
There is no way she should have been able to beat Lila or May.
So, a coordinator that has only won 4 ribbons in her entire career, never entered a Grand Festival, quit, then came back years later and Glaceon who was May's weakest Pokemon and was taking it easy on Dawn (Blaziken or Venasaur would have destroyed Piplup, no contest).
Johanna's won a Grand Festival, but if she pulls punches like May did and uses her weakest Pokemon, then sure she could win.