I have a straightforward question to ask anyone reading these words. Do you think her disappearance is voluntary?
Unless she had a "go bag" stashed somewhere other than her home, I think her disappearance is not on her own volition.
It's pretty much been taken as a given that
--> she walked out with just her phone, no purse, no charger because (maybe) it was in her purse;
--> wearing clothing that would not be appropriate as the weather cooled - no jacket has been mentioned, shorts have been mentioned, tank top has been mentioned, new boots have been mentioned - that might not have been the best choice in runaway footwear;
--> no one has reported seeing her after she left her home - and the text message is problematic.
On the other hand, if she *had* planned this exit, and had things packed and someone supporting this endeavor, she would not want to look like she was leaving permanently. She could have taken her phone as a red herring - it was expected of her to always be carrying the phone, so leaving it behind would have been a huge red flag.
At fifteen, given some of the horrors that have been insinuated, she could very well be mature and forward-thinking enough to leave and go it on her own. Sadly, I don't think that's the case - but I'd love to be proved wrong!