take a warm compress and 3 times a day massage the lump through the warm compress, if its a ***** build up this will help break down the puss and reabsorb it making the lump go away, after a month of doing this if its still not gone make a trip to the vets and request a needle aspiration (they will put a needle into the lump and draw out some some cells/puss and check for bad cells that could be cancer) if the aspiration comes back negative its a fatty tumor and not harmfull, if it comes back positive they will do a biposy.
what colour is your little girl?
hairloss like that is common in blue and chocolates and is colour related alopecia, however if shes not a dilute id have your vet do a skin scrape and a blood test on her just to see if you can find a reason for the additional hairloss.
if it is alopecia its nothing to be worried about, its unfortunatly just one of those genetic things that can happen in blues and chocolates (and merles)
if its mange (another liekyhood for hairloss) then youll need medicated baths to kill the parisite but its 100% treatable! the other thing that can cause hairloss are kidney and liver problems so if the skin scrape comes back negative a blood test should be odne just in case!
Honestly in all that, i wouldnt worry too much about aything, chis are a generally healthy breed, and being shes not even a year old yet, its most likely that the lump is just a ***** absess (especially since its on the neck) and will go away with some warmth and massage.
and welcome aboard Ruby