Sarah's movie career started in earnest in 1997 with two movies, I Know What You Did Last Summer and Scream 2 (Wes Craven's sequel to the 1996 movie Scream).
Over the summer of 1998 in the break between shooting seasons of Buffy, Sarah starred in another two movies, Cruel Intentions and Simply Irresistible, both released in 1999.  This time she played leading roles in both movies.  Although Simply Irresistible, a whimsical romance released in time for St Valentine's Day flopped, the stronger cruel intention was well received if not a blockbuster.