My suggestion is that it is sap. Do you have pine trees or new lumber around where she is? Its being sticky sounds like tree sap. And with this summer heat, the trees will drip sap. If you have fresh cut lumber, she could have gotten sap on her as well. I don't think its an injury. There are no marks on the comb or wattles, just some surface stuff. When you wiped it, did it all come off? Or would you need to scrub it to get it off?
I don't recommend scrubbing a comb or wattle. It can make them bleed. If its tree sap or any other sticky thing, you can get some "Goo Gone" on a q-tip and just rub the sticky stuff off. Make sure not to get it too close to her eyes. When you get it off, you can dry the Goo Gone off with a dry towel.