Your bird is actually a ring-necked dove. They are native to Africa and were imported for the pet trade. They come in a variety of color mutations and are commonly bred in captivity. There are also large feral populations in the US that came from escaped pets or dove releases. If she is white with pink eyes she is an albino, if she is white with dark eyes, she is a white mutation. Ring-necked doves are normally a light brown color. A Morning Dove is a wild species of dove native to the Americas and is not legal to keep in captivity. An albino is possible but would be rare.
As you found out, they will readily breed in captivity. But they need to be in a large flight when breeding and they need to be left alone. It is hard to say why she became aggressive to her mate and killed him – possibly too small of an enclosure or having people around may have caused her to feel threatened. I agree not to get her another mate. The white mutations and especially the albinos can have genetic issues so that may have somehow contributed. She probably is sitting in her dish because she wants to lay eggs again. I would get her a few small food cups that she can’t fit in and see if that solves it. The other cause could be a health issue but if she is eating well and acting well, then it is probably breeding behavior.
Thank you for asking Lafeber,