thats kind of a touchy subject as it still stands up for debate to this day. some believe yes it is herediatary. others say it's an odd form of reincarntaion.however my personal belief as i have seen this happen before is that and person around strong enough energies can pick up on things sooner or later.
a good example is my one friend doesnt practice never has never will. he has been hanging around 4 people who practice heavily and after about 2 years can pick up on subtle thoughts and sense energy.
my other friend whos mother was pagan eventually picked up on things like the family book, familiars,and when she did a ritual.
no real suprise when stuff like this happens. by the sound of thing your mother is part of the gypsy form of the craft which is particularly strong when the mother and daughter are close.