"Mom's not here, she is at work."
Translation:Мамы нет, она на работе.
When «нет» is used with a person it indicates that they are not here.
«Мамы нет» means mom isn’t here.
Scroll down to “Using the genitive case - there is not”
Still not allowed, and yet one of the first exercises in the course disallows здесь нет [some genitive plural] (I forget the noun but it was plural in english, something like "the artists aren't here"). It only allowed [some plural] не здесь.
And then here it's the flip reverse.
and that's the standard answer.
(to clarify, I do think this is the preferred option and earlier in the course it was wrong to reject the other answer