It looks to me like she's getting ready to shed her head area. Once they become adults, its very common for the skin on their heads to take a very long time to begin to flake off. It's taken a couple of mine at least a month to go through the entire process, and you may find that she goes off her food and gets extremely cranky during the shedding process when shedding her head area, as it makes them very itchy and extremely uncomfortable.
The reason for this is that the scales on their heads are much thicker than the scales on the rest of their bodies, and because of that, it takes the new scales under the old skin much longer to form. Also, once they become adults, their bodies provide a build up of fluid underneath their old scales, which is what causes the gray coloring that you're seeing.
This fluid serves to protect and nourish the new scales underneath, as they form.
Once the new scales are completely formed, any leftover fluid will be absorbed by their bodies, and then the old skin will begin to dry out and come off. You may find that it will also take your beardie longer to get the old skin off when she sheds on her head, as the old skin tends to get stuck on their spikes. Make sure that your beardie has some sort of a rock at head level in her tank, or something else that she can rub against to get the old skin off. Also, you may want to offer frequent soaks for 20-30 minutes in warm water, as that will aid in the shedding process.
One thing that I should warn you about, if this is your beardie's first shed, as an adult, is that you may find her basking
under her lights with her eyeballs looking like they're about to explode. They will sort of look like one of those pop-eyed goldfish that you see in the pet stores, only worse! If you do, don't panic, and think that there's something terribly wrong with her, because its perfectly normal. Bearded Dragons have the ability to pop their eyes out like that intentionally, which they do in order to stretch the skin on and around their eyes prior to shedding. Thank God that I knew about it when one of my beardie's first did it, or I probably would have had a heart attack! LOL It looks terrible!
If you click on the "Care Sheets and Articles" link at the top of the home page, and scroll down through the articles, you'll find an article on eye bulging, complete with pictures, so you'll have an idea of what to expect if and when she should do this. We're very lucky that one of our members was able to catch this pic at just the proper moment, as, if you catch them at it, they immediately stop doing it. No one knows why..... just another one of the oddities that make a beardie a beardie. However, I thought I'd better warn you, just in case. The sight of it is enough to scare you to death if you don't know in advance what's going on! LOL