"The kitchen is small."
Translation:La cocina es pequeña.
I dont undestand what your doubt is...
- "La cocina es pequeña"/The kitchen is small
But "Chica" as an adjective is not very common. It is only used commonly in a few of countries.
'Las' is for feminine plurals. Then it would be 'Las cocinas son pequeñas' which would mean 'The kitchens are small'.