I really like this. The hook is solid. The world is created, and I have a good sense of what the protagonist wants. It reads like a chapter, not a story. In fact, it ends with a cliffhanger, not a satisfying resolution.
There is nothing wrong with this setting up a longer story or a novel. Sometimes that’s what comes out.
For a flash fiction story, beginning, middle, and end are required.
Beginning: Hook and set up. We know who the protagonist is, what she wants, and an inciting incident says why now. In this case, Suzana, who has time travel knowledge/power wants to save Ashley’s dad, and the inciting incident is when the means (in the form of the necklace) is found. That’s a good beginning. This part takes at least 495 words. Too long for most flash fiction stories.
The middle is all about meeting obstacles. Usually the most words are devoted to this section. A good practice is to give it at least 500 words (a bit over two pages). I’ve seen 800 words work, but that’s about the limit. The obstacles here are retrieving the necklace intact and keeping it from her mother (and maybe the Certains). The first requires some ingenuity. The second is simply avoided (although there is a plan for burying the necklace).
I’d be generous to call 466 words middle here. That’s with the story over budget already.
The last scene can serve as the ending, but it doesn’t really provide an ending. It sets the two scenes (present and past) nicely and shows time travel is achieved. Then stops.
If you want to cut this down (a good idea even if it’s a first chapter), you might look first at what is not moment-to-moment. My rough guess is that this has about 500 words that could be considered using the criteria I provided.
If I were assigned to turn this into a flash fiction story, I’d explore possible endings first. They need to answer the story question (does she achieve her goal of saving Ashley’s dad?), and might also show her acting in a way at the end that she could not have in the beginning. With a good ending, I’d list possible obstacles and experiment with those that appear most promising.
But my process may not be yours, and I suspect this story is asking to be longer.