Her left eye is swollen and has bubbles and thick drainage, which are signs of a respiratory disease, such as MG or coryza. Get her warm, but be carefull with heat lamps because they are dangerous. We hear of coop fires from heat lamps falling and catching bedding on fire, and some chickens get burned if the lamps are not kept 20 or more inches away. It might be better to bring her inside in a crate or basket.
Do not handle her comb, since frostbite makes them painful. It doesn’t look to serious at this time, and doesn’t require treatment.
I would try to get an antibiotic from your local vet to treat her for possible MG (mycoplasma gallisepticum.) Tylosin (Tylan) is one that can help treat symptoms.