The Science of Love (2005)

Sydney is an ambitious young evolutionary anthropologist trying to find evidence for true love by monitoring brain activity. Her boss, Ileana, is a cultural anthropologist and refuses to accept Syd's line of experimentation. At a party to attract funding for Sydney's research, it's a shock for her to discover she isn't only NOT in love with her fiancé (a computer tech) but she IS completely in love with Ileana, her boss.