I don't think I could call someone a best friend who can't be bothered to find out I'm alive for a period of years. Its not *that* hard to pick up the phone or send a quick message. But it depends on what one means by 'best' friend. To me, that is basically adopted family. Someone who I would get on an airplane for tomorrow if they needed it. But I can count those friends on one hand.
But I agree with the second part of Blue's post. I've got friends I only hear from a few times a year at most. But we make the effort to know we are well, if busy.
That 'ending' friendship stuff sounds like grade school. Unless something specific happened where she decided she couldn't be your friend b/c of it? You'll have to post more info, Prod.
Second thoughts can generally be amended with judicious action; injudicious actions can seldom be recovered with second thoughts.
--Cyteen by C.J.Cherryh