Is your Swiss Mt Dog living in the house in an overheated home and spending minimal time outside?
Mine is a "house" dog but is out most of the day. Her choice. The colder, the better, and the heat in the house can be down to 55-60.
I have had to shut the heat off in my truck and freeze because she is too hot.
How old is the girl? I did observe that my "mountain man", was cold when he was 14 yrs old. Sadly my first Swiss dog did not live to be old enough to get cold.
I have owned mostly big dogs, Akitas and Berners, and "mountain man" was a 35lb mix. They would have all sooner died that be outfitted in a nice warm coat or sleeping bag. Given a choice Molly would sleep out on a patch of ice in a blizzard. She gets PO'd if I make her come in my tent.
I try not to let her play in open water in the frigid temps but in most cases they are solid ice so it's not a problem. I do keep her off icy ponds, lakes, etc. just in case. I had one dog fall in and almost drowned. I don't want them thinking that all ice is safe and forging ahead to meet their demise.
Our wonderful Swiss dogs are meant to keep us from getting seriously hypothermic is we were lost in the mountains in winter. We would indeed be very fortunate to have them along. Big wooly furnaces.
Unless your dog is shivering I would not worry about it. They are designed for ice and snow.
If you are really worried you might want to carry a small closed cell pad for her in the tent but I seriously doubt this would be necessary.
A Swissy has a nice undercoat.
Meet MOLLY