Hi, I was just playing Pokemon emerald and I saw that Wally got a shiny Ralts. Will it be a shiny Kirlia/Gardevoir when it evolves, and I fight him later, or will it just be normal?
No, it would be normal in future battles unfortunately. Rip on the lost shiny.
In the Generation III games, it is also possible for Wally to catch a Shiny Ralts in the tutorial. However, it will not stay Shiny in subsequent battles.
Source: Bulbapedia