Even in the two days prior to her vehicle being found, those closest to her were never treated as suspects. TH and SB should have been! There's no "proof" they were involved because they were never looked at deep enough, and the opposite happened, they were allowed to aid in the investigation. It makes no sense for LE to have allowed that. And it casts lots of doubt on them simply because we don't have enough information!
SB was the first person interviewed. In fact, he was interviewed twice before anyone else was. Did you want them to just stop there and arrest him just because he was her room mate? He last saw her (along with RH) the day before. Several people not only seen her, but spoke to her after that.
They were also going by her work schedule and her phone records. Nothing in those indicated she came home that afternoon. At that stage her last phone activity was 2.27pm. They were following that evidence, not innuendo.
The Zipperer's were also investigated including background checks. They had established with the school that JaZ had been there all day.
TP, her work colleague was interviewed, along with 3 different AT employees.
BC, also interviewed and willingly told them about his relationship with Teresa. Officers even went back and retrieved the "tastefully done" photographs of BC and his ex wife who, by the way, was also interviewed and expressed no ill will against Teresa. They also interviewed the mutual friend of Teresa and BC who said that the 3 of them were good friends.
Lets see, they also interviewed DW who she had also phoned on the 31st, who she had an appointment with on the 3rd but didn't know if she showed up.
They got her bank and credit card records, took items from her house that would contain her DNA, her journal. Spoke with several of her close female friends, spoke with the students she coaches at the high school, drove along several roads looking for her vehicle plus much more...but according to Avery supporter's, they did nothing and never checked anyone in her personal life.
ETA: This was all done before Teresa's car was found.