THE FINAL BATTLE
Switch!
You're playing it safe. Gardevoir's still part Psychic, and that could be dangerous for Dragalge, especially if your rival commands her to use a Psychic move.
Dragalge's tagged out and replaced with the Bug/Steel Scizor That's your combat turn spent, so Scizor's left to take whatever hit's coming.
Turns out it's Psyshock. A Psychic-type move, as you feared, but one that would have subverted your other partner's better defense and hit his weaker one. Bullet dodged.
Steel resists Psychic, so Scizor takes the hit without much issue. He's perfectly fine, but Gardevoir's damn near fainted. Just one more hit, and you know your partner's not one to swap out a Pokémon just because it's on its last leg.
With Gardevoir's lacking stamina, you have two options that'll both take her down. You can exploit the Fairy-type's weakness to Steel with a Bullet Punch, or you can have Scizor attack with U-turn, which makes him come back and tag out with another 'Mon in your party, just to try and be prepared for whatever Gardevoir gets replaced with.