Okay, so I am sure this has been covered, but I have been very far behind and had to skim quite a bit to catch up.
I think that on Monday, Jan 27th she killed Gannon and disposed of his body and the weapon (the 2x4??) in two separate areas. I think that she likely forgot that she was wearing her Apple Watch, so the next day she came up with the idea to rent a car and pretend it was so she could be undercover while searching for Gannon. In reality, on that day, she drove back to the crime scene and relocated Gannon's body. However, she couldn't locate the 2x4, so she had to cut her losses on that.
I believe that she gave her infamous confident interview stating that everyone would apologize to her because she knew that the authorities would track the Apple Watch data and it would lead nowhere. I believe she genuinely thought her cover story for the rental car would fly because AS would back her up, therefore she wasn't overly concerned about it being searched.
I feel like the rental car had some form of DNA belonging to Gannon inside of it and that's how she was charged with tampering with a deceased human body. I believe the tampering with physical evidence charge is due to her removing evidence from the home. I also think there's a strong chance that she had someone along with her on the second ride and that person might be acting as a witness for the state in the future.
Based on her appearance this morning, I think she'll plea not guilty and the testify on her own behalf.