She didn't bring it up in a political context. It was something that first Brown's opposition team dug up and then Trump and then GOP hacks started harping on. SBJJ and other Republicans were suggesting that she thought it would help her political or academic career.
This is why people hate politics, BTW. Here you have someone who is extremely intelligent and highly ethical, was a leader in her field, and is has made a lot of good policy suggestions, and hacks have boiled her essence down to the fact that she once mentioned that she had a distant NA ancestor. Republicans get killed if the discussion is about issues so they always try to make it about identity.