Spanish Citizenship for mother and daughter

Dear Sir or Madam,

I was born in the USA. My mother is Cuban. However, my grandfather and great-grandfather were both Spanish and I have my grandfather's birth certificate as proof. My grandmother was also Cuban however, both of her parents (my great-grand parents) were born in Spain. Again, I have her birth certificate as proof.

From reading all the documents, I understand that my mother should be able to apply for Citizenship as her father was born in Spain. However, will she need to reside in Spain to gain citizenship?

Also, once my mother has obtained citizenship, can I apply for it? If I'm reading the information correctly, I believe I'd need to reside in Spain legally for 1 or 2 years.

Thanks in advance for any help or clarification you can provide.

Kind regards,

Linda