My daughter is also 7, loves to sing and has a great voice.
She's got a guitar and a keyboard to mess around with, but it's mostly me that plays them. We haven't tried music lessons yet. She went to the week long music camp last summer at Village Baptist, had a great time, learned all the songs, but didn't sing at all during the performance. She wants to be part of the worship band at our church, but again is too shy to sing for anyone.
At home she sings (and talks) nonstop. So we just encourage the singing, and supply her with good music to learn. I set up the ghetto blaster in her room, hand her one of my old microphones and let her go to town. She does concerts for all her stuffed animals.
That's okay, you know. Not all great musicians are performers. Composers, theorists, teachers, and even educated audience members are valuable parts of the music community. This is what I'm having to pound into my students' heads right now--even if they put down their instruments at the end of the semester and never touch it again, what they learn as musicians will stay with them for the rest of their lives. They'll never even listen to the radio the same way again.
I had a batch of 7th graders this morning who had to figure out how many beats were in a measure and the values of rhythms. We had to figure out stuff like 1/4 = 1/16 + 1/16 + 1/8. They were able to convert the 4ths and 8ths to 16ths and do the math, but then they were looking at me funny. I said, "What? Have you not converted fractions before?" They all shook their heads. I laughed and said, "I told you this was useful..."