Your mother tells you she is planning a big surprise birthday party for your sister. Your sister will be horrified. She'd kill you if she knew you knew all along. Offer to send out invitations. This smells like a potential family fight, so you're quietly going with the game plan.
Drop hints to sis about dressing up on the date of the shindig.
Two friends are trashing a third pal, saying she's so tight with money, she squeaks. Hey, she did stick you with the bill the last time you two went for margaritas. Nothing like a vigorous bitch session to relieve tension. Nod but refuse to comment. The company CEO is rumored to be romancing a leggy blonde from marketing.