HELP! 9 months pregnant moh

Nicole
Help!! I just found out I'm 4 weeks pregnant (yay!) however my edd is august 3 and my best friends wedding is aug 6.  I am her maid of honor. I'm so afraid to tell her but I need to before we go dress shopping in a couple weeks.  She'll be the first to know since we are waiting to tell my parents on Christmas morning.... I don't know what to do! Do I still try to be moh? Do I back out? Do I let her decide? Ahhhh