In that new Daily Mail article it says, 'It appears she was walking on a path crossing the park,
which she regularly used as a shortcut to home.'
That is presented as fact, so I guess the police have talked to her friends, flatmate, etc. and learned that she did often take that route. There is a bus stop right outside the park gates on Seven Sisters Road, so I guess she would get off there and take the footpath north through the park. It's not exactly a shortcut as going by road seems roughly the same distance, but maybe she was just accustomed to going that way, which would be a pleasant walk in the summer, and saw no reason to use another route, even though it was dark.
From the way the article is written it seems to rule out the possibility I suggested earlier, i.e. that she made it home and then left for Enfield. Perhaps her flatmate was home at the time and has confirmed to police that she never arrived at the flat.