Yeah she changed her name from Yoo Yeon Joo to Yoo Shi Ah around when Oh My Girl debuted and from what I can tell prefers to be called by the "new" nameFun (or unknown to me when this thread was first created in september 2020, over 2 yrs ago):
YooA's real name is complicated ie-
Legal name
Yoo Si-ah (유시아)
Birth name
Yoo Yeon-joo (유연주)
I just learned this fact a short while ago from watching a video of her with Lee Yong Jin(i shd find it again n post it here, since it needs looooads of updates after over 2 yrs of neglect-mianhae yoo yeon-joo )