Growth on guinea's side

[girls and guineas]

My Guinea has a growth hanging from her side. It is transparent--bluish and pink. It looks awful!!
I guess it's a tumor. I'm afraid that it will burst open!! It looks awful!!
I suppose it will kill her, if it bursts!
I don't know what to do for her, that won't cost a lot of money!
Is there anything that I can do?
She is probably 7 yrs old.

 

[BantyChooks]

Pictures?

 

[TattooedChicks]

Could it be a feather cyst?? Any changes recently, drainage from the area, or affected behavior?