I hope the breeders is sending you a new pullet free of charge. This isn't your fault. If you told them you needed them to wait until the Breda were old enough to sex they should have declined to sell you the pullet if they weren't situated with the pen space to hold on to the pullets until they were old enough to reliably sex.
Last year I had one lady who wanted Breda would only take pullets. She was ready to take stock right away but I told her I wouldn't guarantee any Breda pullets until they were at least 12 weeks old. She followed up with me every 3-4 weeks while I was growing out chicks asking if I had anything for her yet. She finally got her Breda Pullets, but not until they were over 12 weeks old.
If anyone is reliably sexing them at younger than 10 weeks I want to know what your trick is.