Confusion

Iam now confused as I have had the result of mum's BRCA test. My mum died in 1995 from ovarian cancer and they managed to get a sample from her tumour and get the DNA out of it and test it and it came back with the same BRCA2 mutation as mine. However all the BRCA 2 diseases are on my dad's side. I've been doing the family history and have got back to the 1700's and found no BRCA diseases on mum's side.
 I have also found another cousin many times removed who has all my paternal grandmother's family in her tree and she has had breast cancer and is BRCA. She is friend on facebook so I've e-mailed her but she hasn't got back to me yet.
 The other day I spoke to my cousin'd daughter who lives in Essex and I haven't seen or spoke to before and we got on like a house on fire she was so like me.