Not an investigator nor a lawyer but as I understand to be incriminated it needs to be proven you did the crime and it depending on the type of the crime it needs to be proven you did it intentionally.

Unless she has anything else to do with the crime a hair follicle isn’t enough to be incriminating, because it alone doesn’t really prove anything. Worst case it just sets her at the scene of the crime and best case the hair is used to narrow down the actual list of suspects.