I felt guilty for exposing her to that. Now I wonder if she would just have had nightmares about something else.
I think if it weren't for the scene in Bolt, it would have been something else. The expression of fear in dreaming would take whatever form it had to work with. Take SheWolfnm's daughter's experience for example. It's odd that a shirt would be used to exemplify the expression of fear, but Jillian's mind obviously tagged it that way. It's possible that some other experience associated with the shirt was what her mind remembered and the shirt was just the associated image.
I've noticed that even when awake, events and thoughts are associated with each other automatically. For example, when watching a scene in a movie recently (a movie which I've seen many times), I was suddenly reminded of a time when I was walking down a street in San Francisco (many years ago). I can't say for certain, but there's a good chance that for whatever reason, I was thinking about that same movie scene as I walked down that street, and the common though linked the memory. It's like smells bringing back memories, except that it's not as visceral of a memory, just a cursory linkage that flashes an otherwise unrelated memory back in mind.