Winnifrith finished behind Mariia Pavlova in the first of Great Britain’s six swimming finals on Thursday.
Winnifrith finished just over three and a half seconds behind Pavlova, who is part of the Neutral Paralympic Athletes and won gold with a world record time of 1min 26.09secs.
In the women’s S10 400m freestyle final, Faye Rogers, 21, finished in fifth place.
Scarlett Humphrey, 19, in her fourth Paralympic final at these Games, finished sixth in the women’s SB11 100m breaststroke final.
Later on Thursday evening, Toni Shaw will feature in the SM9 200m individual medley final, scheduled to start at 17:55 BST.
Rebecca Redfern is in the women’s SB13 100m breaststroke final, scheduled for 18:33, after finishing fastest in her heat. Alice Tai is also in action at 18:56 in the women’s S8 50m freestyle final.