You need to dilute vinegar when you drink it, because it's very acidic. You would put 1 tablespoon of vinegar in one cup of water.
I wouldn't SPRAY vinegar on your baby's scalp or hair, because some of it could go into her eyes.
I don't know how much you'd need to dilute vinegar to use it topically. Why not try rubbing some on your own scalp first and seeing how it feels to you? Maybe dilute it for the baby.
A gentler thing to try would be hydrogen peroxide. Just, again, don't spray it.