The good thing about bringing someone else with you is that they might be able to be impartial and ask questions you might not think of (due to the overload of information you may receive) or they can just be an extra set of ears for you. There is a lot of complicated jargon in the beginning of BC diagnosis and I, for one, needed help navigating it all.
With that said, I did lots of stuff alone when needed. Mammograms, Cat Scan and Pet Scan, - all alone. ;-p Hope you get good results! Love and Luck.