
I use a coat on those dogs that shiver when it's too cold for them. So Dylan, my lurcher, is the only one that wears a coat in this weather! Flash, of similar build being a saluki, doesn't get cold at all and therefore doesn't wear a coat. Neither of course do my long haired yankee and pyr.
So I would just check whether she actually gets cold. If not, there is no reason to put a coat on her.
I do put a coat on three of the dogs when it's snowing or raining because I don't want them to get too wet and then get cold because of it.