As long as your horse has been living in the same location for a year or so, she will adapt well to snow. Ensure she has shelter from rain/wind. Give extra hay (not grain) to provide warmth from digestion on the coldest nights. Get a heated water bucket to encourage sufficient water consumption. I have a 29 year old QH who after several years in subfreezing temps, has developed a very long winter coat. I do not blanket my horses unless they are shivering, which hasn’t happened on over 15 years. Blanketing can be problematic when you have to leave for work in the morning and take the blanket off right at the coldest time of the night so the horse won’t be too hot during the day. As for riding in the snow, if your horse develops balls of snow under their feet because of shoes, I’ve heard putting Vaseline on the soles can help, but if it risks their soundness because it is continually building up on their soles, perhaps it’s best to only ride on trails where their is better footing.