Most female beardies don't start laying eggs until they are well over a year old, same for brumation, but as far as the possibility of being able to lay eggs or brumate, I've seen females lay their first clutches of infertile eggs around a year, but that's rare. It's no different than a girl getting her first period, usually it happens around 12-13 years old, but some girls don't get it until they are 14-15, some get it at 9-10. It just depends. Contact with a male dragon is not necessary for them to lay infertile eggs, and they also typically lay multiple clutches, so that's something you need to be aware of. It's rare that they lay only one clutch and they're done, it's usually 2-3 clutches back to back. My very first girl laid her first clutches at one year and two months old, and she laid 3 clutches.
Typically the baby beardies at pet shops are around a month or so old, and at 5.5 inches long, it sounds like she was a little over a month. That's pretty standard. And the biggest, healthiest beardie I have ever had came from my local Petco, she is 8 months old, 19" long, over 450 grams, and has never once had any illness, parasites, etc. So it really is just hit and miss as far as pet shops having sick animals, they are all franchised and all run by different managers, employees, etc. I know some are just awful as far as taking care of their live animals, do the key is really checking out all of the animals, the cleanliness of their tanks and cages, etc.
As far as brumation, it's rare that they do it before a year old or older, but it does happen occasionally. I've heard of 6-8 month old beardies going into brumation, but the problem with brumation is that it is too often assumed as a kind of catch-all by people, who may or may not have a sick beardie, but they just automatically assume it's brumation. So I really don't know the legitimacy of people saying that their 6-8 month old beardie went into brumation. Usually they are over a year old, and it typically happens during the Cold months, having them go into brumation during late fall/early winter, and waking up early spring. Some beardies do not ever go into brumation while in captivity, it's dependent on their enclosure environment, the temperatures, the lighting, etc. There are a lot of really great articles on here on brumation if you search. There are a lot people that prevent their beardies from ever going into brumation, some that have beardies that do it every year, etc. It's a topic, much like the egg laying, that is very much worth doing some research and reading about.
