My cockatiel layed eggs in winter what do i do?

i bought a female cockateil about a year ago - i bought a male about 3 months ago - she is hand reared he is not - sometimes they get along other times they dont. i put them in an avairy during the day and bring them in a night time - this morning i found an egg in the cage, in tact....anyways i put it in her nesting box ..(.the past week or so she has been constantly in her box with the male sitting on top and last night when i went to bring them inside she attacked me ...for the first time...) anyways she is in the box with her egg and i think another one is coming cuz i think i can see a huge bulge in her chest , i dont know whether to leave them outside now because i dont want to disturb her and her eggs but im worried they will get sick or die from the cold because they are not used to it ...what do i do? do i bring the birds inside with the eggs? its the middle of winter -