It's A Mall World After All by Janette Rallison

Charlotte is not the best perfume saleswoman in the world, but her job at Bloomingdales does have one advantage- it's view of the mall's courtyard. Charlotte can people-watch and pretend she is writing her thesis on the psychology of shopping and what your purchases say about you. Unfortunately, one afternoon Charlotte sees her best friend's boyfriend Bryant and his best friend Colton meeting girls at the mall, neither of whom are Bryant's girlfriend Brianna. Charlotte is outraged at Bryant's behavior and in shock when instead of dumping him, Brianna accuses Charlotte of trying to break them up. Charlotte is determined to discover what Bryant is up to, but her attempts are always disrupted by Colton. Rallison has created another light-hearted, humorous romance. The crazy situations that Charlotte creates combined with her quick wit will make readers laugh out loud.