The woman was driving south of 272nd St. in a 1992 Honda Civic when her car struck the 2000 Chevrolet Malibu which was parked on the shoulder of I-5, after 11 p.m. Saturday.
The impact pushed the Malibu into a ditch and onto its top; it then spun around and came to a rest facing east, blocking two lanes of traffic. The car was totaled.
Four people inside the Malibu, a 33-year-old woman; and three children ages, 12, 8 and 6; were injured and transported to St. Francis Hospital in Tacoma.
The driver of the Civic had minor injuries and was later booked into the King County Jail.
The cause of the crash is still under invesigation and charges may be pending, the Patrol said.