Does she have a coat and some booties? Some dogs don't tolerate boots, but if she can get used to them, it might really help.
Our Grace is a little put off by the temps, too. If it's -20°F or below, she doesn't want to go out at all. I just keep telling her to 'potty' and we stay out till she does--she's gotten to the point now where she knows I mean it and she doesn't dilly-dally.... She doesn't tolerate booties, but she's more willing to go out if I put the dog parka on her.
"We are--each of us--dying; it's how we live in the meantime that makes the difference."
"It's not what you gather, but what you scatter that tells what kind of life you have lived!"
"Be kinder than necessary, for everyone you meet is fighting some kind of battle."