You definitely need to train up some of your Pokemon.
If you can, try to get a Flame Burst up to destroy the Field and burn it, I forgot who on her team uses Rain Dance, however.
As for your Noibat dilemma, I'd recommend getting a Pidove and training it, cuz Air Cutter's a really nice move to have it. Has STAB, Super Effective, and hits both Pokemon!
Try to Paralyze that Yanmega, then you're free to throw anything you want at it. Worked for me in my older playthrough.