Rheumatoid arthritis since age 17 here.
She could try cutting out nightshades (tomatoes, potatoes, etc) from her diet; that tends to be one of the more scientifically supported things to try. I've heard of people cutting gluten or dairy from their diets with good success too, although I'm more inclined to consider that a placebo effect. Glucosamine and fish oil are generally good for joints. They won't magically make it go away but could provide a little relief or less damage in the long term.
There are MILLION scam holistic remedies for arthritis, most of which won't do jack. Don't jump on those too fast; they offer a roller coaster of hope and disappointment that will wear you out really fast.
I would guess that the treatment she's being offered is something like metholtrexate, right? The description you provided could really fit nearly any RA treatment; since RA is an autoimmune disorder all functional treatments suppress the immune system to some degree. That's what you want. I remember reading "sudden death" as a side effect on the mtx warning and thinking, "isn't that more of a main effect?"
She shouldn't be afraid of the medical treatments they're offering. Methotrexate and naproxyn really got me back on track, able to use my hands and walk without a limp again. I'm on Enbrel now (same class of drugs as Humira, as mentioned by SlowSpyder) and I LOVE it. Yeah, the side effects lists of these drugs look a little scary, but honestly it's not anywhere near as bad as the disease itself and they can be really effective.
[edit] For you mj fans, there's not much that mj would actually do in this situation.

Save it for the folks that really need it.