Circumstantial friend....

I have a friend whom I love to death but I don't understand her at all....  She seems to only have good intentions.  She seems to have my best interests at heart the way a BFF would.  But, she is really only supportive when my life is in shambles and not going good.  She supports me through the bad times but quite literally disappears during the good times.  I find this to be rather annoying.