I haven't found my 2 greys to be bothered by mirrors at all. In fact, I had one installed in a spot not to be mentioned......... and when Talon first saw it, she looked up at it sideways for a short time, looking at herself as I talked to her, didn't seem to care, just looked around at everything else she saw in it, and then continued doing her thing. She does see herself in it a lot, but she looks, and then moves on to attacking whatever else she's interested in.
My other grey has yet to notice it. But she doesn't seem bothered by mirrors at all.