This is from the previous thread so I was't able to quote it properly. This was written by bsublime?-my apologies if I'm incorrect.
There are multiple ways to weave your hair:
Sewn in: Your hair is cornrowed and the wefted/track extensions are sewn to the cornrow using thick thread and a curved needle. The needle goes through the cornrow, not the scalp lol. Usually the majority of your hair is cornrowed with only a small portion of the top, and possibly the edges left out to blend with the extensions for a more natural look.
Glued in: The hair is left free and parted, hair bond is placed on the weft of the extensions and placed on the scalp until dry. Another way is to cornrow the natural hair and bond the extensions to the parts of the exposed scalp between the cornrows. Once again, the top/front and/or the perimeter of the natural hair is left out for blending. There is also a way to bond the extensions by cornrowing all or most of the natural hair, and a stocking cap or 2 is placed over all of the cornrows(to protect the hair) and the wefts are glued down to the cap using hair glue/bond.
Fused/bonded tips: This is the least likely way black women put extensions into our hair, IMO. Small bundles of keratin tipped, loose extension hair is bonded to very small portions of the natural hair at the root using a special heated tool. That is done throughout the hair leaving usually the top and edges free to blend. (A la Britney Spears a couple of years back with the choppy visible extensions)
Based on the pictures of her at Liberty, I would guess her extensions were sewn in, in one of the ways I stated above. According to other pictures of her, she changed her hairstyle pretty often and it would not be worth the 100's of dollars charged just for the fused tips to be put in, not even including the cost of the hair itself. So yes, it is very plausible that the strand of hair is Alexis' and not a strand from her extensions. Yes, weft/track extensions tend to shed, just like natural hair. The fact that at least a portion of her natural hair was left out means that the hair found is from her natural hair. JMO.
My apologies for the lengthy lesson on weaved hair. If I wasn't clear on how it works I'm more than happy to clarify!