When skin heals with scar, some pores and follicles can be blocked, with a resultant white buildup or oil, skin cells or calcium. These can exfoliate on their own over time. In a cooperative patient, they can be easily lanced and removed, but that may be a little difficult in your 6 y/o. Some acne medicines, such as tretinoin or salicylic acid, can also help to exfoliate these bumps if they persists.
I would hold of treatment for now, as they are likely to disappear with time. If they become a concern to your daughter, and she is requesting treatment, consult your dermatologist for either the topical treatment or to have them lanced.
These look like milium, clogged sweat glands. Happens in areas of trauma or scars. See a dermatologist and they can remove them in the office pretty easily, but they should go away on their own over time. Best, Dr. Emer.