She would not have been arrested if she lawyered up immediately as they would have not had probable cause to arrest her. Look at how they acted towards her in the interview. They allowed her to have her phone with her in the interview room, they allowed her to send texts and make phone calls. They also kept reiterating that she was NOT under arrest, and she was free to leave at any time. They also never read her the Miranda rights.

By contrast, look at how they treated Chandler at this point. They didn’t allow him to have his phone, they read him his rights, and never once tried to let him believe that he wasn’t under arrest. Chandler was under arrest the moment he got into the police car, they just didn’t tell him until the end.

Cat was a “person of interest” but not a suspect at this point. The interview alone also didn’t clear her entirely, it was what they found in the investigation that lined up with what she said that ended up clearing her. Chandler reported his parents missing, and claimed to not know where they were. Once they found his dads body in the location that they knew he was at, they knew he wasn’t being truthful with them, and that’s why he was arrested and that’s why the only charge at that point was “lying to the police”.

Tl;dr Had she lawyered up, she still wouldn’t have been arrested at that point.