@Adirondackwannabe, why should she take into account which shoes he prefers? If she wants to wear heels, she should. If she wants to wear flats, she should wear flats. His preference is irrelevant.
I agree you’d assume he already knows he’s shorter than her, and there’s no evidence to suggest he might feel intimidated by her towering over him in her heels. If he does get upset about it, she’ll know he’s an idiot and she can be busy next time he calls. Some men would find her height sexy I’d imagine.