I am so sorry for your experience with Whitney.
I have no idea how my team of 5 Lv. 19s and 1 Lv. 21 (Togepi) was able to beat her.
Granted, I lost all my healing items in that match and came just single-digits away from death, but I am happy that my first run is going well.
Unfortuantally, This will likely make any loss worse :(