Translation:my grandmother Samia
Why isn't "My grandmother, Samia" correct?
It should be جدتي يا سامية then, afaik.
Why wouldn't it be "My grandmother is samia"?
It can be that, if said independently. It is not very common tho, a better way to say 'My grandmother is Samia' would be:
جدتي هي سامية