DD 8 MO hasn't woken up from her 4:30 afternoon nap

[Buthewasstillhungry]

I'm worrying and telling myself not to.
She isn't ill as far as I could tell but has been asleep since 4:30. Normally she wakes after half an hour then goes back to bed for the night at 7ish.

Do babies sometimes just sleep for longer?

Is this just something that sometimes happens?

TIA

She probably just needs the extra rest, but I'd wake her, otherwise she won't sleep tonight (and nor will you!).