That information was already confirmed to be incorrect. She was not born in May. If you are going by Kol's statement in 4x03 that was a continuity error.
"This is madness. How can a 16-year-old girl shake the entire French quarter?" - 1x11 (Klaus about Davina)
" I'm gone not three months and look at the trouble your in". - 5×12TVD (couple weeks after 1x11 Rebekah to Matt), she had left at the end of Summer right before he started college in 1st episode of season 5. 3 months after August/September is November/December)
"They've got every **16-year-old girl** in our coven dying to be one of the four chosen for this crazy-ass ritual". - Sophie to Marcel in flashback **8 months prior to 1x02 which took place same time as 5x01 in September** (end of summer/starting college), September minus 8 months is January.
^ these dates confirm Davina was 16 between January 2011 to November 2011. Putting her date of birth between November 1994 to January 1995.
If it was May 1994 then she would have been 17 when she 1st appeared, despite it saying multiple times she was 16. If it was May 1995 then she would not have been 16 at the Harvest, despite it being said in flashback (1x05) that she was.