Shame on you Bandit, making her go out in the cold in her bare skin.
It's best to have layers on. Thermal socks with a good pair of boots quick release if poss.
A pair of jeans is fine provided you have thermal longjohns on underneath (tights don't cut it)
T shirt, fleece and a good jacket, down filled is best. Finally a wooly hat is a must as are insulated gloves of some sort.
You must take your boots off when entering anyones house and you will want to take a layer or so off while you are there. If she has that lot, even if she feels the cold, she should be ok down to -30
Just a thought. She needs to make sure she has, or gets, some waterless face cream.
Most skin creams contain quite a bit of water, which is not recommended at those temps