I really feel she went missing on her run. That's why it was only 15 minutes long (if that indeed a fact).
All her jogging gear was missing and she's not going to sleep in it.
I think the wording of Mollie going out for the jog between 7.30pm and 7.45pm led to uncertainty over whether it was a 15-minute jog during those times or if she left the house at some point during those times to go for a jog, and the time the jog ended has not been made public. I think it might be the latter explanation.
Mollie's mom said in the early days that she and Mollie were texting about dinner around 7.30, and in the recent ABC video interview with DJ he said that he and Mollie were snapchatting up to around 7.30 before she Mollie went for her jog (I'm paraphrasing but that's what I recall the essence being).
So if Mollie's chatting until approx 7.30pm, then she might have had to go get changed into her jogging gear before leaving, which would put her leaving to go jogging somewhere in the 15 minutes just after 7.30pm approx.
One of the articles said that Mollie's jogs were usually about 30-45 mins? I don't know where they got that estimate from, though. So that would mean the jog would probably last from around 7.30-8.15 or even.
I do agree about not sleeping in the jogging clothes, unless she got back and fell asleep on the sofa? But I'd think even if that happened she'd wake up in an hour or so and later get a shower and go to bed properly.