I have lots of thoughts on this, having fought my way through this issue repeatedly as my body changed through menopause.
I usually spend a fair bit of time on my posts, and am careful with what I say. I don’t have that time right now.
(Quick aside: “excessive amounts of B12” is only what can be measured in serum. B12 isn’t stored in serum, so this is slightly irrelevant if her body isn’t using it well. She might need co-factors–other pieces of that puzzle. This includes but is not limited to lithium (orotate), folate (bioavailable forms only), carnitine, potassium.)
Also note that what you don’t take is as important as what you do. If you are one of the large percentage of population for whom folic acid paradoxically blocks folate absorption, not taking FA is essential.
My guess–and this is ALL my guess; without being her, or being in her body, it’s anyone’s guess-- is that she is right: it’s hormonal.
The medical establishment is not good at supporting women in menopause. To put it mildly. (I deleted a rant here.) Tell her it’s not her imagination if she feels medicos are discounting her symptoms.
Here’s where I’d start, if I were her advisor: vitamin D, magnesium (anything but oxide), and pregnenalone, all OTC. I do not recommend exact doses unless I have a direct connection with a person. If she’s not taking these, I highly recommend she does.
If she’s not on bioidentical HRT, I recommend she find a provider who can support that. Specifically Estridiol/E2 & progesterone. If she doesn’t want to do that for some reason, I might have further suggestions.
Without knowing more, that’s as far as I’ll go.