When she gets married, first of all your best friend wants you to get married too. She starts lecturing you about your future life, about social needs, about kids. You two get different topics to talk about. Your old talks about crush and about make-up all got a new turn. However you still are happy for your best friend at the end that she got married finally.
When your best friend is married and all of sudden you feel like you have nothing to do in this world. You feel alone. You realize that she never let you feel the absence of a life partner. You have been shopping, eating, dancing, crying, laughing, cooking, back biting, and dish washing, sleepover with her. She has been in every aspect of your life.