Susie, AVMs have progesterone-receptors, which makes them respond to hormones. But, if your AVM didn't act up dramatically during your three pregnancies, I do not think that hormone replacement therapy would kick it into high gear. Also, it is different taking hormones when you are not producing your own naturally than it is to take additional hormones when you are already producing them.
About your daughter, I think you should look into the possibility that there may be HHT in the family (http://hht.org/)
, which is hereditary and can predispose people to multiple AVMs.
Incidentally, after doing much research, I no longer believe that AVMs in general are not hereditary. If only 20% of AVMs ever become symptomatic, and they were not diagnosable in the pre-MRI era, then it would be easy to miss a genetic connection, wouldn't it? Especially if it takes a group of genes rather than a single gene, so that only certain family members carry the right genetic combination to predispose them to AVMs.