You are assuming that Cheryl had an opportunity to draw blood from the person who interfered with her life on Monday, Feb. 8. I don't see that as a typical option for someone whose life is about to involuntarily end.
Suicide strikes me as absurd and the theory was started in response to the "self-inflicted wounds to two fingers". How someone goes from two self-inflicted finger wounds in a possible abduction / murder to suicide is beyond me, especially given that the alleged suicide was in a road-culvert / drainage-ditch.
Is there anyone alive who can say that if suicide is the decision, an under-road culvert that also serves as a drainage ditch should be my last memory?