These look to potentially be hay mites (static lice is not a term which is used anymore).
What product did you use to try to treat them previously? Was it prescribed by a vet?
Was it done as part of the correct length course dosed by weight?
Please do see a vet to get the correct course of prescription strength treatment. That is three separate treatments with two weeks between each treatment. So a total of six weeks to treat them. Given she is only six weeks old, she is barely old enough to have completed one full course of treatment.
If you had used an off the shelf spot from a pet shop, then they are usually not strong enough to fully deal with an infestation. Often they will suppress but the mites usually then come back.
You will also need to fully disinfect the cage and all items and ideally change your hay source. F10 is the recommend disinfectant product.
New Guinea Pig Problems: Sexing & Pregnancy; URI, Ringworm & Parasites; Vet Checks & Customer Rights