Not PTF, but I don't think she ever left the condo of her own free will. I think they had some help and I think she was taken to a planned upon location and killed. I'm not sure what they did with her body, but I think it's a location over which they had/have control, and/or could be certain there's little risk of her being found. I would not be surprised if she was killed near the M's property, and is perhaps hidden in that area. I won't publicly speculate further, but it just seems to me that this was such a personal thing for TM that she would prefer a location that was familiar and where she felt safe and aided by a trusted third party or parties. I also think TM would prefer to have others in deep with her, to protect herself from turncoats who might be motivated under pressure to throw her under a bus. if you're in it together, you're pretty much sworn to secrecy from all angles when it comes to what you really know and when you knew it, or noticed something that could be useful to LE. And, I think she's ultimately a coward who couldn't have done this on her own, without drama, and without making sure the responsibility was shared. JMO.
I've also wondered if there is private property in another area with which the M's have ties and where a third party providing help could have traveled with no one being the wiser. Particularly if the timeline is off and by 3:41 it was all over, as I suspect was the case.