Juvenile Vaginitis can be common, but I would be wary of making sure it is not also an infection. Check her temperature at least twice a day because she could become heavily symptomatic in a matter of hours if it is indeed infection. Her temp should be between 99-101 F.
You can rub neosphorin if it is only juvenile vaginitis because I think it's basically bacterial infection of the vulva if I'm not mistaken, a surface infection. But if it spreads into her urethra you are taking a huge chance of her getting very sick, and those infections are very painful. I understand you don't want to use antibiotics if at all possible, but there are precautions you can take to get her to the vet to be sure she's ok. Bring towels to lay on the table, make sure all employees wash their hands or wear gloves who touch her. Strip off your clothes and shoes, spray your shoes with antibacterial, ect. Believe me, I've done it when I had to.
I am also against over vaccination - but I do think there is a fine line between putting a pup at risk of disease and ensuring they do not get vaccinosis. Titer testing is the only way to be sure. If her temp goes up, don't take any chances and get her in right away.
If she does have a UTI or infection in there, there is no way to cure a UTI as far as I know of besides giving antibiotics- you can help prevent them with supplements, but if you find other ways please share.