It may be worth taking her to your MCHN or pharmacist - if its bacterial, then there's stuff that will clear it up in a flash, but if its not then there are other products around.

Some people use cortisone cream but I don't like using that unless neccessary - my fave tip for nappy rash is to use MooGoo Soothing MSN cream on it, clears it up overnight. If you're using cloth nappies, try using a raw silk liner as they have antibacterial and healing qualities.

If you're interested in MooGoo (and trust me, it works!) then check their website for the stockists in your area. They do mail/internet order but that can take a few days to process.