I thought I recalled that KG's and MM's families were very close? The girls had been friends forever but I also thought the families themselves were close.
So I could easily see them navigating this tragedy together and sharing whatever information they have between them, including comparing each daughter's phone records.
Maybe that could also explain how SG might have seen the injuries on MM's body, if the two families went together to view them, and maybe to support each other they stuck together and both viewed each girl together.
About those last phone calls to J -- I do wonder if there were no voicemail messages left? If not, I don't feel 100% certain these were unrelated calls. Could the girls have heard noises downstairs or even seen someone walking outside, entering the house etc, but for whatever reason they didn't think they needed to call 911 but were worried enough to call J?
I half wondered if they were inadvertent "pocket-dial" calls during the attack itself, but for both phones to call J seems unlikely.
Or, maybe the girls saw the police lights at the Band Field incident and were calling J about that? (to see what he knew or to make sure he wasn't involved)?
MOO