How do you feel about, can you afford to take her to a poultry trained veterinarian?  It sort of looks like something that might need to be lanced?? 
I have had a doctor tell me before that "when you have a "lump", or "pimple", or a sore sort of might be a boil coming on thing, that you put a hot, moist cloth on it.. warm compresses."   You know, run a clean cloth under the water until the water is hot, wring it out, hold it on the sore lump... repeat, do this for 15 minuntes several times a day..   it will either "come to a head" or "go away".
I honestly don't know what that is..   it looks like it could contain something...   maybe she got stung by a bee and the stinger is in there, or something like that?   And, it does look as if it could contain pus..  (or a parasite)? 
If you can, first choice would be a veterinarian.  If you can't..   you can see and feel it, we can't...   warm, moist compresses until "something changes"....     it looks like it's not IN her ear, it looks to be just below it..  though it maybe be IN it, you can tell better.  
You say she has no mites or lice on her?  You checked for that?  And, have you wormed her?  When, with what?  How does her poop look?  What, if anything changed a couple of months ago ..    has there been any change in feed or environment, or anything different that would have, could have caused her to "not feel well", to not be thriving?  Is she molting?  Is she laying?  When was she, did she stop and when?  All this more about her overall health than her "lump".
Or, neosporin on it, and oral antibiotics for her until it clears up or changes?
 
Well..     Just some general suggestions are above... some thoughts....  other than that use the Search here on BYC and search for any possibilities or symptoms and read up..   maybe something will come up that relates to her problem or problems.
 
Best of luck..   take care..  she's a pretty girl, I hope she gets well.