He uses her Pokéball

Suddenly Alex had a realization. If a Pokémon is caught then only that Pokémon can enter its Pokéball. No other Pokémon should be able to get inside. If he just tries to put his pal back in her ball he'd quickly be able to figure out which of them is the real one in no time. She may have started to prefer staying outside of her Pokéball in recent time, but this was for her own good.

He grabbed her Pokéball from his pocket and tried to aim it at the two Gardevoirs. Their constant teleporting made aiming difficult however, but he tried to be as steady as he could.
Then they finally lined up and he placed his finger on the button.

"Gardevoir, return!"

A red beam of light came out of the Pokéball and went right for the Gardevoirs, who could immediately tell what he was trying to do. They tackled each other, desperately tried to push each other away, both reaching out for the red light, only for it to graze both of their fingers.

In a flash of red light the two seemingly disappeared, which confused Alex. Did one of them teleport at the most opportune moment? There wasn't a way both of them got in the ball, was there?

In truth, there was.

A Pokéball wasn't known for being spacious but with two Gardevoirs instead of one the space was actively quite cramped. The two were **** to sit with their legs wide open and bending around each other's backs, forcing pussies to occupy the same place and chest horns to stab into each other. Each Gardevoir had her head on her duplicate's shoulders, sadly **** into that position to conserve space.

A position like this would make it hard to exit the Pokéball, nearly impossible even, so their only method of escape would likely be getting sent out by Alex. Unfortunately for them Alex seemed to have no idea of their situation, so the two were likely to be stuck like this for a while.