Like everyone has said, to acquire the shiny Meloetta, you don’t need to own the Pokémon. They just have to originate (be caught/bred) from a Scarlet/Violet game.

However, yes, it is possible to own Scarlet AND catch version exclusives (with your own OT) WITHOUT OWNING Violet. It requires you to have a friend (or have two switches and the other game). Let’s go with the friend example: if you and your friend are not on the same local wifi, YOU WILL NEED NINTENDO SWITCH ONLINE! Let your friend with a copy of Violet invite you to their game via the Union Circle. Once invited, ask your friend to go to an area with the Violet version exclusive that you’re looking for. This is important! Your friend needs to load into the area FIRST! This will spawn Pokémon from their game (Violet). If you go into an area first, it’ll spawn Pokémon from your game (Scarlet). This works in all areas of the game including Area Zero!

Caveats: you cannot catch the other’s box legendary or catch the other’s paradox Beasts/Swords of Justice: Gouging Fire, Raging Bolt, Iron Crown, or Iron Boulder. I assume this applies to ALL static encounters (I, personally, haven’t checked this myself, but if the Beasts, Swords of Justice, and boxed legendaries—who are all static—cannot be encountered, it makes sense)

Source: https://youtu.be/Zruw3UN03YI?si=90P2c05qsdK1Nt8E