Do deer like mums or are they one of the few plants that they won't eat?
As a general rule, deer won't eat chrysanthemums. But it's really up to the deer. Like people, individual deer have specific tastes. I don't like sauerkraut, for example, but friends of mine do. Most deer may hate chrysanthemums, but there may be an odd one or two that like them.
When you're trying to find deer- or rabbit-resistant plants, you'll need to learn largely by trial and error. (Though deer-resistant plant lists are always a great place to start.)