I can't find any sources that point to the meaning "Fairy Princess", and other meanings are unknown, so I was determined to discover the authentic meaning myself. I may be very close, if not spot on to showing how Tatiana actually means "Gift of God". Here is what I found: "Tatiana is the feminine form of the Roman name Tatianus, a derivative of the Roman name Tatius... Tatius is Roman family name of unknown meaning, possibly of Sabine origin."Could there be a link between Tatius (Possibly Sabine - which spoke an Indo-European language, and was located in ancient Rome) and Tadeo (Italian version of Thaddeus)?If Tatius is a Roman family name spoken in Indo-European language, and if you combine "TAD"eo with Thadd"EUS", would you not find a link between the two?If and when you see the possible correlation, you will notice that Thaddeus is from the Greek name Θεοδωρος (Theodoros), which meant "gift of god" from Greek θεος (theos) "god" and δωρον (doron) "gift". May be a stretch, but it that is how words, names and languages are formed. This is the only relative source of a real authentic meaning.
I'm not sure of the accuracy of this, but I've been reading that Tatius is possibly derived from the Latin tata meaning "father". If this is the case, it seems that Tatiana then would either be Tatius replacing -us with -ana to feminize it, or a smashing together of Tatius and Ana.
Macedonian: ѕа-ѕи-ја-ниа (tza-tzi-ya-nia)
English: ray-rays-god-our
Modern: Our god rays light.