Gelfling, there is nothing odd about your story, and it does not offend. The same kind of female jealousy over hair, leading to curses of envy, including curses by touching and curses by the evil (envious) eye, are found in my own Sicilian family. It is one reason that many Sicilian women of my grandmother's and great grandmother's generations wore bandanna-style head scarfs when they went to market -- so that no one could see or comment on their hair and thereby curse it.
Normally, i would say that a client would need a reading to confirm the question of whether a curse was cast by a remote means such as doll magic, or mal occhio (the evil eye) was given, or a curse by touching the hair was made -- but i think you already know it happened, and how, and why, and by whom. So save the reading money and accept this as confirmation that i, at least, believe you and agree with your disagnosis and your identification of the culprit.
The hard thing is that once a curse like this starts to working, it actually affects your body's physical systems. In the same way that a curse on a man to have a heart attack will actually give him real heart disease, so will a curse for brittle, thinning hair actually give you brittle, thinning hair. Maybe there are underlying genetic tendencies toward this in your family, maybe not, but even genetics can only show tendencies, and it takes an event or a "something" to turn the genes on and off -- and there you are: that something was a curse, or envy.
Unfortunately, i know of no magical means to make your hair grow thicker and less brittle. You already know all about good scalp care, how to use oils and conditioners to keep the hair from drying out and breaking, and which methods of hairdressing are easier on the roots and cause less damage to the hairs themselves.
I can tell you that it is traditional both in Sicilian American and African American culture to use rosemary herb tea in the shampoo and/or rinse water (instead of plain tap water) to aid the scalp, and that oil treatments based around herbs (Like Hot Six Oil, to name one brand) are often helpful. You probably have already heard advice to use only natural products -- stop using anything that has chemical names in it, and i agree with that advice 100%. But, sadly, once the follicles wither, it is almost impossible to grow them back.
Good luck to you, and if you have to wear a weave, wear it with pride -- because when you like what you see in the mirror, you'll know that although your enemy may have won the battle, she has lost the war -- you still look good and feel good, and that's what she lacks.