My grandma's further gone than that, but she sometimes remembers my mom's name, at least. Doesn't remember us "kids" though, me and my siblings. Doesn't even remember her own husband, my grandfather (he died a long time ago though). :/
That's why it's hard for me to watch this video because even if it's a happy sight, it reminds me that it's only temporary and not necessarily a sign that she's getting better. Even minutes after that she probably doesn't remember her name again. If you catch it early, it's treatable, but if it's gone too far you can only watch them become less and less the person you knew and more and more a shell of a person until there's basically nothing left.
I apologize in advance since I had no intention to ruin anyone's mood with this post. I've just had too much first-hand experience with this condition to feel optimistic about it.