Shaista is a Farsi and Kurdish name for girls that means "worthy", "deserving", "virtuous". It is not an Arabic name but since the meaning is good Muslims can use it.
The Kurdish pronunciation of Shaista is (SHA)rp + (YI)ppee + (STU)n, with the syllables as Sha-yis-ta, with the stress on the first syllable (the Sha- part). The Kurdish version can also be spelled as Shayista, Shaaista, Shaayista, Shaesta.
The Farsi pronunciation is like the Kurdish one in pronunciation and syllables, except that at the end the name is pronounced with a teh sound, not ta, as in (SHA)rp + (YI)ppee + (S)weet + (TE)nd. The Farsi version can also be spelled as Shayisteh, Shaisteh, Shaesteh, Shaistah, Shayistah, Shaistah, Shaestah.
Shaista Maryam is an acceptable combination.
Shaista is spelled as شايسته in Kurdish and Farsi. The Kurdish pronunciation is correct to use in the Farsi language as well.