Congratulations to you and Walter. The blood will wash off in some hot water, and I would probably save it if it was my first ever egg, but yes you can eat it. The eggs will probably get a lot larger in a month or two. Is Walter closing her beak now? LOL
She is probably hot. Most chickens will try to cool off in hot weather by panting and some will hold their mouths open. Placing a fan in the coop and providing shade, and cool water all day will help.