Hi Eugene,
This is a rare exception when you can say
Elle est une ...
when there is an adjective
but it is safer to say
C'est une bonne cuisinière
as we have so many mistakes when il /elle is followed by a noun and you just cannot say -
Il est mon oncle -----> C'est mon oncle
elle est ma sœur ----> C'est ma sœur
I have encountered rare cases in novels when for instance a mother is complaining about her daughter ignoring her she will say to show indignation -
Elle est ma fille après tout
which seems to emphasize the fact relating the parentage between the mother and daughter rather than just a statement. You could almost put a swear word in English before daughter to convey the indignation.
Hope this helps!
