I DO believe she can be allergic to all (almost all) brands and colors. There are some ingredients that can be very problematic that are used in ALMOST EVERY SINGLE LINE AND EVERY SINGLE EYE PRODUCT.
I'd bet money that she's sensitive to bismuth oxychloride, which is a natural mineral derived ingredient. It lends shimmer and a smoothness of texture. She could also have a sensitivity to a colorant, like carmine (natural red pigment) or the D&C dyes. Red pigment is used not only in red and pink colors, but in blue, purple, brown, black, peach, coral, some greens, and on and on. Pretty much the whole rainbow *possibly* could contain carmine.
I agree with the suggestions to try mineral shadows - and to look specifically for those that DO NOT contain bismuth oxychloride.
My own experience is similar to your mom's - I didn't wear shadows for almost 20 years because I was plagued with significant contact dermatitis, red, itchy, weepy, crusty, oozy, painful rash on my lids. Drs. just told me to use cortisone cream, which offered minimal relief.
To soothe her tender skin, I'd recommend using emu oil (find it at health food stores) since it is naturally anti-inflammatory and very healing. It's often used on burn victims and really helps to minimize scarring and to promote healing. Have her avoid all makeup products on her lids until her skin is smooth, supple and comfortable again. THen consider trying mineral makeups, but be sure to read the labels, since many of them are based on bismuth.
(And to clarify, I am not saying that bismuth or carmine are bad ingredients and should be avoided - I think for most people they are fine, and we even ingest them in natural foods. But if you are sensitive or allergic, it's a whole other story.)
-b.