Andersen was raised in Seattle, Washington with her two older brothers. She trained as a dental assistant, although she did not like working for dentists. After she turned 30, Andersen felt that she might have the "life experience to string an entire book together."
Her first novel, ''Shadow Dance'' was published in 1989.
Her novels are known for being funny as well as containing "sexy sizzle and great characterization." She has been nominated three times for Romantic Times Magazine's Reviewer's Choice Awards, winning in 1998 for Baby, I'm Yours. She has also been named a Romantic Times Career Achievement Award winner. She has appeared three times on the list of 10 novels picked as Amazon.com Editor's Choice (in 2001, 2002 and 2003).