If she aborted her pups then I feel it was natures way of saying she wasn't ready for these pups. Have you since had her spayed? As she is a pet there is no reason for her to left intact. Spaying her will elimate another accidental breeding and unwanted litter. Also if left intact there is always the possibility of her developing a Pyometra after/during each heat cycle,which is most often fatal if not caught in time.