If this link works. I did a search on "petmate 70401d chicken coop". You can get these at Tractor Supply so it looks like YPiedra is in the USA.
https://www.tractorsupply.com/tsc/product/petmate-superior-construction-chicken-coop-70401d-1428968?cm_mmc=feed-_-BingShopping-_-Product-_-1428968&msclkid=61d9ef053a811d4bd9008d25ebbb7190&utm_source=bing&utm_medium=cpc&utm_campaign=Shopping - All Products&utm_term=4585375807245420&utm_content=All Products
Yeah, 3-1/2' x 6' at the most. I don't consider the enclosed coop section as really separate from the run section as long as they have access to both. I could not find the size of the enclosed section but it looks like it's only 3' long and 12" of that is taken up with the nests. It is easy for that pullet to block access to the nests.
YPiedra, one rule of thumb on here is that you need one nest or every four hens so you should only need two nests. Almost no other person would have the trouble your having if it wasn't for the attitude of that one pullet. Just rotten luck on your part. They each have their own personalities and you can't tell what a living animal will do.
Not sure why your pullet is doing that. My guess is that she is still pretty immature and is establishing her dominance over the others. Where is your food and water? Sometimes they intimidate the others by trying to keep them away from food and water, especially when integrating. Going through puberty may be close enough to integration. Is she actually blocking access to food and water? Hopefully the immediate fix is that easy. An actual photo of your set-up might help us see something.
She may grow out of that as they all mature. Maybe. A temporary fix could be to put another nest in the run to see if the others use it. Don't use cardboard if you have rain.
Where are you located? I'm interested in your weather and climate. That could make a big difference in my suggestions as to a permanent fix. If you modify your profile to show that information it's always available. Location makes a difference in a lot of things.
If bad weather means a blizzard, tornado, or hurricane I can understand. But don't worry about heavy rain or something like that. Let them decide if they want to be outside. Mine often enjoy a rain, even a heavy one. They are usually out foraging for worms that come to the surface.
With them free ranging all day every day what you have should be OK for the good weather months as long as they have access to it and are not locked in that tiny enclosed area. That's why I'm interested in where you are, what does bad weather, especially winter weather, look like?