not really sure I understand - you think being in a choir might not make much difference to how she sings, is that it? Don't know how that could be the case unless it was one heck of a crap choir really.
Depends on age a bit too. Dd goes to a fab choir. I would not honestly say she has a breath-takingly beautiful voice solo and neither do a lot of girls but when you hear them singing TOGETHER after instruction, it sounds magnificent. I think it's quite amazing to hear the effect a choir has.
I've found it helps with training the ear. A lot of singing must involve listening to yourself and dd has to do this (in theory at least) for violin too so spin-off effect is beneficial.
Singing generally is good exercise too - lungs. And it looks like fun. You should see the beaming faces of those girls when they run off after choir practice still singing. I don't know maybe there are bad choirs, am not great judge of singing myself but I think the benefits are enormous actually.
Ours do warm ups (fun), scales (they don't seem to mind it), learn new songs and work on them and it doesn't seem a trial at all. Sounds good when they are all singing together and it is less intimidating for a child than singing alone in front of a teacher. To sing well you need to acquire a few skills, in a choir you'd learn how to sight read music presumably if you did not know how, you learn to hear and recognise notes and hear whether you are in tune or not, you learn to blend in with other voices, where to get your voice from (ie preferably not pressed out off the throat), how to articulate when you sing and how to project your voice- all sorts of things.
Why not try it?