I used to live around Lakeland florida, and people used to get ducks for their kids and when they for big would just let them go at any lake they find. The ducks all seem to survive and do fine. Some mate with wild ducks and other with the other ones that were just dumped. I think if there are other ducks around it should be fine.
Could be an ancona duck. Can't see super well, but she looks like mine. Or she could just be a mixed domestic. As the person above said, sometimes they do fine, but that also depends on how cold your winters. Mallards migrate when winter hits if you are more northern, but most domestics can't. Where i am, most domestics die in the winter cause they cant find enough food or they get too cold or both.