Regarding the questions about why an arrest has not been made in this case:
I'm certain most people here know this, but some seem to think it's not complicated. In order to make an arrest, you have to charge that person with a crime or crimes. Otherwise, the arrest is a waste of time. In order to charge a person with a crime, investigators must have probable cause. In this case, enough strong evidence tying said person to the crime. Often, when time has passed between the crime and an arrest, the District Attorney is consulted regarding charges. The DA reviews the evidence outlined in the arrest warrant and charges can either be accepted or denied, based on a prosecutor's ability to build a reasonable case against the defendant. Almost always the DAs office wants to be confident of a conviction before the charges are ever made.
This isnt a TV show where the detectives follow bloody footprints to a suspect with "creepy eyes" and cuff him at the 28 minute mark before credits roll. The investigators are building a case. It takes a mountain of man hours to sift through phone data, browser history, travel records, surveillance footage, blood and fiber analysis, prints, background searches, on and on. It could take months or even years to build a case if they have not yet found strong evidence pointing to a specific suspect. All of this has to be done while other crimes are being committed or worked on. A person has lost her life, and anyone charged with her murder could also potentially lose their life or freedom. They arent going to arrest someone just because the public is getting impatient or because a bunch of us think weve got it all figured out. Thats not how it works.