It was Summers-Newton’s second medal of the championships after her gold in the SM6 200m individual medley on Tuesday.
Grace Harvey finished fourth in the freestyle, missing out on a bronze medal by 0.01 seconds.
Eliza Humphrey, 19, made her international debut at the event and won bronze in the SM11 200m individual medley.
Great Britain are third in the medal table with 14, behind Italy with 33 and Ukraine with 32.