I self inject B12 weekly for weakness, muscle cramping & pain. Not sure specifically how it works, but I know when I’m not taking it. I have a chronic pain condition RSD and I am allergic to most pain meds. I also get cortisone injections every 4-5 months.
But I’d guess she was taking the B12 for energy, to combat fatigue.
I take 1000 mg B12 everyday because in my blood work it was very low.
A good friend of mine has RA and has had some major setbacks in life health wise, financial-wise and deaths in the family. She was beyond sad, with good reason, and her doctor gave her a B12 shot. It was life changing. She is now in a completely different state of mind, very positive, and looks forward to things that used to seem overwhelming and impossible.