Shamsiyya
No. The root sh‑m‑s (شمس, 'sun') appears in the Qur'an, but the specific feminine name Shamsiyya is not a Qur'anic proper name.
Yes. Shamsiyya and its variants have been used in Persianate and Pashto-speaking regions as a poetic feminine name formed from Arabic/Persian linguistic patterns.
It carries Sufi-inflected imagery because the root 'shams' (sun) is prominent in Sufi metaphor and because of the historical Sufi figure Shams Tabrizi, though the name itself is not tied to a single saint.
شمسية
Yes. It is rare and poetic; families seeking a devotional or luminous name often choose such forms.