If the redness was spontaneous then possibly - but if dd has been scratching then I would be inclined to put the surrounding redness down to that. Does the area feel warm to the touch? difficult I know in this weather but is it noticeably warmer than the surrounding area?
The slightly yellow tinge looks like normal ?fresh? scab to me ? infected pus would be more greenish and smell disgusting.
No medical training by the way ? just a lot of experience with someone scratching at their skin and infecting it