Well, I'm not sure how much I can ease your worries, but perhaps I'll "bump" your post up so it gets more attention.
The "white" color you mentioned, sounds like a shed which would indicate she is growing. Have you seen her shed before? She does sound a bit on the small side, but my two are a little larger than the "average" beardie...and older now. Are you measuring her from the tip of her nose to the tip of her tail? Beardies do have different growth spurts, so it's really not "fair" to compare her to your other beardie. However, there may be something wrong with her diet or lights that are causing this.
To know for sure, I'd need to get a general idea of your set up and lighting. Beardies need UVB rays (there are several different kinds) to help them digest their food, absorb Vitamin D3, and for many other reasons. Is she thin? Does she have any "bumps" or signs of curving in her spine? That would indicate metabolic bone disease, which could cause stunted growth and many other problems. It is preventable if they are getting the correct UVB rays. Do you know what light(s) you are using and how far away she is from them? (The distance she needs to be from the light will vary with the brand and type of light, some UVB lights aren't really healthy for beardies, too, so this is important to know). What are the temps in her cage and what type of thermometer are you using to measure them? (Many don't give accurate readings).
Also, what is her diet consisted of? Live feeders? Greens? And are you dusting her feeders with vitamins and calcium? If so, what brands/kinds? And how often?
This is just a short list of questions and things to consider...there's a much more detailed "list" of questions (I believe it's under Beardie ER or Health) that would help determine the problem, if there is one, if you don't mind filling it out. I can copy and paste it here if you can't locate it.
I'm sorry I wasn't able to offer more advice. Try not to worry, there are many helpful people on the site who will be able to offer more insight.
I hope everything is ok with her,
Abi
