salaamz I got this reply for you from someone who wishes to stay anonymous
It is about anonymous and the vaginal infection.
All vaginal infections that require an aplicator signify bacterial infection with secretions thus to avoid nullification of Whudu, she should wash first then apply the medication and then use a wing pad. After perform her wudhu perform Solat and after she may dispose of the pad which would again nulify her Whudu. She should also wear a pad at all times to avoid contaminating her clothes or body which would then require Ghusul.
I'll just add to that, not all vaginal infections requiring application are bacterial in nature, since viral, protozoal and obviously fungal which is the most common and can be a direct result of being on an antibiotic or even simply being a diabetic can trigger it.. I'll assume the procedure above is the same for all, I can only comment on things medically but not from the stance of Islamic jurisprudence..
If the infection is indeed fungal then I'd ignore the applications and request a single pill treatment, it is better than the 3 or 7 day applications and far more effective especially against some of the more resistant strains!
and Allah swt knows best