My vagina has one longer labia minora than the other, is this normal?

Probably normal.: If there are no other symptoms and this has been longstanding it is probably normal. No one is ever perfectly symmetric.

Likely normal. : Paired body parts have natural variation. Ask your gynecologist to be sure, but you are probably perfectly normal.

Probably Normal.: Some asymmetry is quite normal. If aesthetically or functionally "symptomatic", labia minora reduction surgery may be the answer.