Well, Éowyn, it might not sink in for her that quick, and might take a whule, as it can in real life. Perhaps soon after something could happen, (or even a moment of silence could happen) which causes it to all sink i for her.
Also, having her sometimes act as if her parents were still around could be one thing, sometimes - I know when my granny died I had dreams where she was still around, and asked if she was coming to visit once at lunch because I'd forgotten. And someone I knew mum died and the nedxt day he was wondering why she hadn't prepared his breakfast, when he remembered and it all sank in.