It looks like a classic electro-forged Schwinn frame.
The fenders, chain guard, chain ring and seat match the 1952 Standard Schwinn for Girls.
Or the 1953 Schwinn Meteor for Girls
Schwinn used the same frame for several different models within a year and over the years. The models were made different by adding a tank or lights or a rack.
1957 was the last year for the support bar between the top tube and the down tube.