I can see lines in the air, they are vibrating yes. As I mentioned, just check for eyesight issues. If everything is fine no worries at all.
While imagination is an essential aspect of childhood and children imagining things around 3-5 years old we can’t deny unseen as we are not only physical but spiritual beings as well. Children are more sensitive to this. The most important thing is not to exaggerate and deny it or worry. Better to do something interesting with her and not focus on it.
If she would tell something else and more or continuously I would consider then. Especially if there are many more signs like nightmares, weakness, headaches, indigestion ect. Even I would pay attention to general her wellbeing at home and school.