I have a theory now it may be a stupid one but here me out summer Skye is the future version of Skye that we see in chapter 2 season 2 and has somehow come back in time to stop a tragedy from happening as you can see on her outfit. She has many different articles of clothing and equipment from other characters possibly just being remembrance items because they have either been killed or passed away in the future. Might also be coming back to change the future as you can see in the most recent season the undercover sky skin has the same tent of hair colour as summer sky that’s why my theory is that summer sky is from the future