Sister Diagnosed

Hey all.  My sister was diagnosed on August 1st of this year with IDC stage 2 HER2+.  She is undergoing chemo and is having a double mas when chemo is over.  I have been doing a lot of research and came across this board.  I have a few questions, it's all a bit overwhelming.  First of all, her genetic testing came back negative, thankfully.  I was wondering though, could I be a carrier still?  Like I said this type of cancer is new to me so forgive my questions.  Would I have necessarily gotten it first if I were the carrier?  I should mention she is only 40.  I am 37.  There is no family history of bc that I am aware of, but there are many other types of cancer in the family.  We have had every type of skin cancer (my mother included), on both sides.  My father died from Merkellcell Carcinoma.  My cousin on my father's side had cervical cancer.  I do believe there has been colon cancer and a few other types (my family isn't exactly close).  Next, I know I am above average risk, although not high risk.  I have yet to get to a doctor since her dx.  What is the most likely scenario as far as testing for my future goes?  Yes, I know it would be easier to pick up the phone and ask, but I just moved and don't yet have a doctor here.  I appreciate in advance any advice/comments.  Thanks