I do NOT recommend anything from a department store. You will get a much better bike if you buy used.

Bike fit is really important and can make all the difference of whether or not you will keep riding or not. Test ride a bike before you buy it, or you can also get a good idea of your bike size by going to a bike shop and test riding several bikes. That way at least you know if you ride a 15" or if women specific design is comfortable for you, that sort of thing. Then even if you can't test ride a used bike you have some idea of whether it might fit you or not.