Your sister-in-law needs to be evaluated and treated by a Lyme-literate doctor (LLMD). Non LLMDs have no clue about this horrible disease or its complex treatment!
A LLMD is one who has treated Lyme disease and the co-infections which come with it for many years and has gotten patients well. A good one will follow Dr. B's Guidelines, the "gold standard" for Lyme treatment.
Unfortunately, LLMDs are far and few between. She needs to go where they are. At least half of all Lyme patients travel out of state for their care.
Most LLMDs do not accept insurance due to the politics surrounding this horrible disease. Read poster TF's explanation, "Why Lyme Doctors Don't Take Insurance":
I was told doctors in CO do not treat aggressively enough, because CO is extremely tough on any doctor who does. The medical board is relentless on them. Posters on Lymenet from CO recommend going out-of-state to see a LLMD.
When she calls for an appointment, ask if they have any cancellations or a waiting list. Patients have been able to get in sooner by doing this.
Have her read the books written by the top LLMD, Dr. H titled, "Why Can't I Get Better?" and "How Can I Get Better?". They are an excellent source of information.
Also read "Cure Unknown" by Pamela Weintraub. Check your local library or buy it used on Amazon.