I have a question about Makoto's 3rd leap in time

I love this film, but there's one thing I still don't quite understand, even after multiple viewings. When Makoto leaps back in time for the 3rd instant, (the 1st being her encounter with the walnut time travel device in the science lab and the 2nd being the train incident), she runs across the field, jumps over the river and manages to leap back in time into her house. She checks the fridge and notices that her sister has yet to eat Makoto's pudding. As she's about to eat it, her sister and parents come into the house and as she hears her sister is about to have it, Makoto says the line "There's no way you're getting it! This is mine!" As soon as she says that, Makoto instantly disappears and re-appears in the future during the point she made her 2nd leap, as her jump across the river continues and she falls into it.

So my question is this. How did Makoto disappear like that? The film clearly establishes that in order for her to time leap, she has to gain speed and momentum beforehand, whereas she was stationary in her house and yet somehow managed to disappear and leap into the future and even the pudding she was holding disappears as well.

Does anyone know how to make sense of this scene? Like I said, I really do love this film, but this is the only scene that I have yet to comprehend.