Based on my childhood I would not suggest that you worry too deeply about it. Instruct her, but don’t make it a big deal. Like “don’t forget to say ty” vs “what do you say”. One comes off harsher and while autistics can be dense on somethings, not everything. Anxiety can be reinforced by having to much pressure on people in general. Autistics often need more time to adjust and adapt.

If you are a polite person she will learn by your example afterall.