Born Margaret Chan in Texada, BC, Canada. Mother Patricia was a teacher, and former stage actress, her father Harry (Chinese), a car salesman. In the mid 1960s her mother divorced and moved back to Texada Island, British Columbia, to live with Tilly's grandmother, and later the family moved to Victoria. Raised in British Columbia by her mother and step-father, Tilly started taking dancing lessons at age 12. She earned a scholarship to a top ballet school in New York. At 17 was connected to Connecticut Ballet Company and later Throne Dance Theatre, but a serious back injury ended her dancing career. She then went to Los Angeles to pursue an acting career. Tilly made her first film appearance in a bit as an auditioning dancer in FAME (1980). She made a short appearance in "Hill Street Blues" (1981), and began her career as an actress [dancing not all forgotten as seen in THE BIG CHILL and PSYCHO (both 1983)]. Next step was her casting in Academy Award buster AMADEUS (1984) as Constanza, but again her body interfered and seven weeks with her foot in a cast were more than the backers could accept, and her "compensation" with a role in Forman's next project VALMONT (1989) didn't do her career much good. However, she did meet actor Colin Firth during filming, and they had a son in 1990. From 1989 to 1995, she averaged a movie a year, and with the exception of LEAVING NORMAL (1992), without anything remotely equivalent to her potential. Other notable credits include OFF BEAT (1986), MASQUERADE (1989), THE TWO JAKES and CARMILLA (both 1990), BODY SNATCHERS (1993) and SLEEP WITH ME (1994), along with several appearances in made-for-television movies. Sister of actress Jennifer Tilly, in 1995 she retired from acting and moved to British Columbia, Canada, to devote herself to writing and raising a family. She has written a novel titled Singing Songs.  Nominated for Supporting Actress 1985: AGNES OF GOD 1 nomination