Scaly mites can be fatal but only if really neglected and not treated for a very long time. She doesn't look that bad in the photo, really (considering that even healthy female budgies have pretty crusty looking ceres).
I would NOT go ahead and add a dog/cat medication. The medication used for mites in birds is the same as what's used for fleas/ticks in dogs (usually ivermectin), but you could risk seriously overdosing her if you just put a drop on her skin. After all shes around 1/500 the weight of an average dog.
You'll have to take her to a vet and the vet will probably give her an injection so she can be sure to get the right dose.
I would NOT go ahead and add a dog/cat medication. The medication used for mites in birds is the same as what's used for fleas/ticks in dogs (usually ivermectin), but you could risk seriously overdosing her if you just put a drop on her skin. After all shes around 1/500 the weight of an average dog.
You'll have to take her to a vet and the vet will probably give her an injection so she can be sure to get the right dose.