There is an official touhou game that you play as flander

[Koa]

It's called moedan (see at theend of intro to touhou)

[Drunken_Flower]

nnnnnnot exactly

Moedan is a fangame for training your Danmaku dodging.
why use flan? i dunno, probably cause she popular.

for now, no playable flan in any official game. she do appear in StB and VD, but as boss.
and obviously she appear lotta in fangames though