It will not hurt the baby. The crop is the part of the chick that holds the food before it is digested. It is just below the throat. It will have a whitish milky substance in it. You can see it from the outside. No need to pick up or touch the chick. I am sure your mom is feeding her baby and will feed any more that hatch. The will be fine with her sitting on them, that is how she is keeping them warm.
It the daddy in the picture. He should be helping by feeding her and maybe even feeding the baby.