Q. My alsation has got a enlarged mammary gland (only one) could this be a phantom pregnancy as she has never been bred
A. It sounds more like mastitis. Phantom pregnancy usually cause milk production, nesting, unusual behaviour. Mastitis or mammary glands mass often is limited to one gland only. The gland may discharge milk or watery fluid, it is hot and painful .Dogs suffering from mastitis often have high temperature and are generally unwell (off food, lethargic, weak). If you take her to your vets they should be able to make diagnosis and give her appropriate treatment.