So sorry your sister is dealing with this! I've had tinnitus since I was a teenager - it was a manifestation of my hearing loss and quite annoying.
I just stumbled upon some info on the BetterHealthGuy site (great Lyme resource) that I also learned through research. If you scroll down to Dr. G's comments, you'll read:
"Ringing in the ears may be related to Babesia or viruses."www.betterhealthguy.com/integrativetherapies
Lots of other great info shared by noted LLMD's (and ILADS co-founder Dr. B ;)
You might consider trialing 1 drop of Cryptolepis tincture (major player in Buhner's Babesia protocol). If your sister responds to it in any way, that's a sign she's dealing with Babesia/Babesia-like infection....very, very common coinfection.
It would then make sense to expand the protocol to include the other things Buhner recommends. There is overlap between the Babesia and Bartonella protocols (Alchornea, Sida Acuta, Red Root, L-arginine and Hawthorn) so it wouldn't be too hard to cover a few more bases.
Moderator - Lyme Forum
Jul '14 started what proved to be inadequate treatment ala PCP day after nymph deer tick bite
Sept '14 met LLMD - clinically dx'd with Lyme due to Bells Palsy - confirmed via CDC positive WB
Feb '15 transitioned off abx and started full Cowden protocol along w/LDN
Aug '15 started transition to Buhner's Lyme, Babesia & Bartonella protocols
Nov '15 stopped LDN - 98% healed!