of course it goes, with the right management. if it's bad, i'd speak to your vet about it. otherwise, clip off feathers and wash throughly with specific shampoo for the problem, carefully pick off all scabs, apply recommended cream, keep legs scrupulously clean and dry.
if you can't bear to clip off the feathers, there are other ways, i believe... pig oil and sulphur rubbed in etc is supposed to be very good.
Grrr, just wrote a really long reply and then very cleverly deleted it!
Firstly I would cut off her feathers so that you can treat it more effectively and her legs will dry faster, but obv. this is personal preference. Then I wash the legs thoroughly but gently with cold water and Hibiscrub (warm water allows the bacteria to reproduce faster) to make sure they are really clean, then allow them to dry completely. Next cover the area completely with a barrier cream such as Sudocrem(great because it is antiseptic aswell), which softens the scabs and prevents further mud and wet getting to the area. Some people cover this with cling film and bandage over the top to speed up the scab softening. Once the scabs are soft and ready gently remove them so that the bacteria cannot live underneath. If it is really bad you might need to speak to the vet and get antibiotics.
It is then a matter of once a week washing well with the cold water and hibiscrub and afterwards covering with a barrier cream of some sort or alternatively using turnout sock type things. It is important to try and keep the legs as dry and clean as possible. There is an arguemet as to wether or not to hose the mud off each day or to brush it off when its dry, personally i think if the mud is really wet its doing no more harm to wash it off but otherwise leave it to dry and then brush it off.
Mum's horse had it a few years ago, he had never had it before and never had it since. He had just been put in a different field (next door!) which had different soil. His was really bad but it cleared up pretty quickly.
Id trim off as much feather as she'll alow (be careful, if the legs are sore sometimes even the most polite horse will object), wash wth dilute Hibiscrub or Malaseb then rinse & dry thoroughly.
When her legs are dry apply some sort of ointment for mud fever. My favourite is Equine America's Fungatrol ointment but other people at my yard say they've had good results with udder cream (nearly got me kicked, apparently his lordship thought it stung, & I wasn't allowed near his legs for a couple of days), Sudocreme (pretty similar result but I was allowed near provided I didn't have cream) & Dermolene cream (works for us if it's just a mild dose).
If the field is muddy it may be worth stabling for a few days until her legs are starting to heal up.
When it's cleared up keep a close eye on her legs for any further flare ups because it's far easier to treat if you get it early. Some sort of barrier cream or oil to protect the skin from the wet can help stop it getting hold.
Are you sure it's mud fever & not greasy heels? What do her legs look like?
wash with hibi scrub pat dry apply a product called de scab by nettex leave on for five mins then rinse pat dry again put some flamazine on you can only get this from the vets do this twice daily for about 3 or 4 days and it should be clear if not keep going if there is lots of mud in yor field section it off if your horse dont like stopping in th stable!