I keep a container of washed playsand in the female's cage all the time for egglayers.
You said..."she was already producing eggs when i mated her? Therefor it must be unfertile...Will she produce more eggs ?"...I can't tell you how far along she was in her cycle when you mated her. If she was quite far along she could dump a clutch of infertile eggs before the normal 30ish days from mating....followed by a fertile clutch up to the normal time later. If she was not quite so far along when mated, she could lay a clutch that is part fertile and part infertile at about the 30 day mark...followed by another part fertile and part infertile about 30 days after that.