This is an opportunity to continue teaching her sportsmanship and teamwork. She'll have good days and bad days, but you'll have to keep hammering some things home every single game.
By the time she's 7 or 8, she'll either be taking it really seriously, or she'll be into something else. 3 1/2? You're lucky if she isn't sitting on the ground pulling out grass.
At that age, my kid was only there for the snack at the end of the game.