I'm not sure of exact size she needs but the 4 sq ft inside most people tend to go with it would have to be 3x4ft. I currently have 5 hens in a 4x6. If i was her i'd make it bigger just in case should would ever add more. Which is what i wished i would have done in the first place. Plus mine is raised about 2 1/2 ft off the ground which is good since they also have a dry place outside to hang out if its snowing or raining.
sorry I just built mine. I seen alot on amazon and ebay but the prices just seem too outrageous. If you don't wanna build it maybe try and find a local construction worker, even after you'd pay for materials and them it'd prob still be cheaper and built better then one you can buy. Just my 2 cents. And just a side note my pit mix is named luna too.
I don't have a specific company for you except maybe the cottage company in Ohio. Those are some well built coops. Just google the name and will come up for you (sorry i don't know how to link stuff here yet) They also make sheds and playhouses.
Most of ready to go coops you will see on line are going to be made with really light, flimsy, fir wood because it is easier, cheaper to ship, so be careful when looking. I have one like this and it is "OK" for me because I live in CA, where cold and snow is not an issue. Even with that I am having to do quite a bit of work to make it more secure
Another choice might be to convert a really sturdy shed from one of the home improvement stores? Sorry don't have more to offer, I really just wanted to reply to give you a heads up on the material used in the pre-mades, they also really exaggerate how many chickens will fit in those things. Mine claimed 4-6 standard sized and in actuality 3 will be on the 'cozy' side if you know what I mean!