As I recall, the mirror thing is in the book. Dracula comes up behind Jonathan when he's shaving and Jonathan is shocked to see that Dracula has no reflection in the mirror.
I think the mirror thing also had to do with the fact that vampires supposedly lacked souls, which doesn't really follow logically, but since when were superstitions logical?
As for Lucy being more attractive than Mina . . . well, in the book, Lucy was the one who had three
suitors competing for her hand in marriage. And the one whom Dracula went after first.
Lucy was always the prettier, flashier one. Mina was the smart, sensible one.