You have to decide quick either to stop her on her tracks immediately or walk with her. Both can work, the former less often, the latter more often.
= full stop = it's very hit or miss cause you have to do it very decisively with 100% conviction. think of how like you would stop your friend passing by who didn't notice you. assertively, not aggressively.
important: if the girl is clearly in very good mood your chances are higher. if you both lock eyes from the distance then go for hard stop ASAP. if she's walking toward you and you catch her attention [point at her or wave] from distance [3-5 meters] then you also have better chance to fully stop right away.
troubleshooting: if the girl stops for a second but you notice she's about to start walking past you then immediately you have to slowly start walking backwards to walk with her, either slightly ahead of her on by her side. never behind her, never chase. not fully stopping might be caused by confusion or not knowing how to handle the situation so don't take it that serious.
= walking with = approach from the side. say something. do your best to focus her attention on you. try to walk slower and slower and see if she follows. keep talking until you see her eyes light up and starts slowing down adapting to you. then stop walking. and move her to the side where pedestrians don't bump into you.
in general the point of the daytime approach is to stop a girl to be able to talk like humans do. do all you can do to stop her. walking with her by her side is not meant to last too long, it's just meant to give her bit more time to see you're cool so that she can stop and talk to you.