I think the dairy theory applies to me. I grew up on a diet that included very little dairy, I'm caribbean so we barely ate cheese and yogurt when I was growing up but some butter every now and then. About 5-6 years ago I started eating a lot of yogurt and I think it contributed to fibroids for me personally, but in your case, since you eat a lot of fish, perhaps your liver isn't dealing with the excess estrogen your body is producing and that's why you and your mom are making fibroids, who knows, just an idea.
I'm trying to find the right solution.
Have you had your hormone levels checked? Like estrogen levels and such?
and have you been tested for any hepatitis, like hepatitis B or C, if it's been more than 20 years, it may not show up in a blood test, but still maybe take milk thistle anyway. The best kind is from eclectic Institute, they have no fillers.
I wish you success in ridding yourself from fibroids as I wish for myself.