BLUE TONGUE SKINKS

I have a young Halmhera Blue tongue skink. She is about 3 months old, 10 inches, and 55 grams. Is this a good weight? I feed her a little over a teaspoon of food every other day but she only eats about 1/4th of it. Is it just her own growth rate or could there be something wrong?
She in a 20 gallon with a basking spot that gets 100 degrees, and heat mat on a thermostate that's around 95 degrees for nighttime heat, a large water dish, and a cold hide. She's on aspen chipped bedding. Her diet is also a balanced blend of premium dog food, veggies, greens, and some berries.
The photo is her right after she ate...

Size and weight sound perfectly normal to me. Some grow faster, some slower; yours may be a bit on the slower side, but nothing I would worry about at all. If you'd like to have her grow a bit faster, maybe decrease the amount of veggies and greens you add to the dog food --maybe even give her just plain dog food until she's gained a bit in size. It may make her a bit more enthusiastic about meal-times. And it may not. But maybe worth a try?

On another note: I do not think your skink is a Halmahera; it looks like a Merauke to me...

How long are you leaving the food in for? Is the area the skink is in quiet?

I find shy skinks tend to come back to their food when they know the "coast is clear". It can take minutes to hours, depending. I also have found out that if you warm up the dog food just a few seconds (slightly warm to touch; NOT hot), I get a better feeding response. I'm guessing this is so due to the dog food becoming more smelly than if it were at room temperature.

Good luck to you and your skink. She doesn't look bad anyways, so I wouldn't worry much. And Susann is right, this is a Merauke.