Are you sure the white blob isn't urates?
She isn't shedding much because you're not feeding her much from what I'm reading. At 300g she should be on something like weaned rats. A mouse every week or two is far too little for her.
At this stage in her life, you should be aiming for 10% to 15% of her weight in each meal. So for a 300g snake, 30g to 45g in each meal.
If I was responsible for her feeding, I'd be feeding her a weaned rat every 5 days. As she gets bigger increase the size of the food, at 500g drop off to feeding her once every 7 days.