Outside of her main party she only has Victini (which is not an actual member of her team, she never even caught him, he's more of a traveling companion)!

But I guess you could also consider Briar's experiments as Pokémon that she legally "owns", although most of them are not ready to battle and are contained in her lab. So, in that case, two other Pokémon I could mention are Type: Null and Eternatus.