No you cant "tell her off".
She is ND, and likely telling the truth about how she felt in that moment. Whilst its not what you'd like to hear, it really is a silly thing for an adult to take so sensitively and personally from a child they KNOW to be ND.
Whilst to you "see you soon" is just an pleasant way of saying goodbye, to an ND child they may well have no concept of such bullshit social nicety/norms, and soon is such an abstract subjective term.
She may well be told by other adults, parents, teachers etc in her life that something is happening "soon" in response to struggling to wait her turn for something, or dinner nearly being ready, or moving on to the next task etc and therefore interpreting "soon" as literally imminent!
And if you'd been there a while, maybe she had had enough and wanted her own space back to "normal"? It doesnt mean she doesnt like you. You just are interpreting it from an NT perspective.
It's the double empathy problem
Haven't you ever wished someone would go, or suggests doing something sooner than youd like or you need a break from? Difference is you've probably learnt when its appropriate to keep stuff to yourself and when its rude, and have developed the communication skills to advocate for yourself if something is not for you.
At 9, children are still learning that, NT and ND!!
If she says similar again, rather than taking offence, maybe talk to her about it, find out what she actually means and how she is feeling. You may be surprised that it's nothing personal AT ALL.
From an AuDHD adult who had lots of experiences as a child like you describe, and spending a lot of time baffled as why despite "always telling the truth" and "replying when I was spoken to by grownups" was i still always in trouble. And as a result grew up thinking I had to make sure I always said the "right thing" and was responsible for keeping everyone else happy.
Trying to see things through her eyes would be amazing for her.