It sounds to me like she is unnerved by the reflections, just as she says. GT kids sometimes get really focused on something and it's hard for them to shake it, even if they know better. DS4 is scared of his room even though he KNOWS there's nothing scary there. And I have a vivid memory of when I was little and realized that "going #2" made noise, and I got sort of freaked out by that and refused to go #2 in public restrooms for several years. (Perhaps TMI, but hopefully useful to you!) Kids are like that sometimes.
I wouldn't make too much of it. I'd respect her worries as best I could without accepting them as realistic. Reassure her that it's safe. I suspect she'll get over it fairly quickly if you neither stress over it nor minimize it.
You might also ask her if there's anything that will make it so that she can walk on the reflections. Maybe if she watches you do it first? Or if she can try just one step and then go back if that's too much for her? But you may just have to wait it out.
On the bright side, I'll bet you dollars to donuts that she won't still be doing this as you pack her car for college, so don't let it trouble you too much!
