Her phone records for that day were shown briefly on Gray Hughes' yt channel. At around the time she turned around she tried to contact her ex. There's no indication that she spoke to him or that he made her change her mind.
So far, we don't have proof that the ex was aware of her presence in the building. The person from her second to last phone call alleges that she mistook him for her ex, asking where his apartment in the building was. The last person to talk to her over the phone claimed that she sounded confused, not knowing her whereabouts. We don't know if this was before or after she was seen sitting next to the car and crying. It would be interesting to know if she was still on her phone at that point. She was calling the ex constantly until her phone activity stopped, but he didn't seem to have picked up. I don't see why she would climb into a car trunk, if the purpose of her visit was to confront the ex about something (a possibility). The only other option I see would be running away from police after the road rage incident that happened an hour earlier. If they had no contact the ex wouldn't have known about it and couldn't have planned for her "rescue".