My thoughts ... Totally planned!! Why? Who knows!! A psycho who keeps journals and such is hard to understand. Men are ... Men. Maybe she found an old message or picture from Heather and it fired her up. Maybe someone mentioned seeing Heather, and she was so jealous that it set her off. Probably, Sidney is the only person who knows other than Tammy.
Sidney calls and whimpers and manipulates Heather from payphone. She calls her bff and struggles with this all ... SM leaving wife. She agrees to meet him at PTL to talk. I think she sees his truck and gets in, with only SM visible. She gets in with purse, phone, keys, and is talking when TM attacks from back. SM speeds off while TM is strangling, hitting, suffocating, .... TM is way bigger and has advantage at this point.
I think someone else helped dispose and/ or come up with alibis (including phone, purse, etc).
I think Heather is close to PTL and Moorers' house ...
What about septic tanks? Do dogs detect on these if a body were in it? Sorry if stupid question ...
I thing the Georgetown "shooting" was verified by others in car, but I don't doubt The MRS. Herself set it up and possibly TGIF incident. She is clearly warped!
All just my thoughts on all I've read ... Praying that Heather is found soon!!