This is kind of nit-picking, though. If she can fly, and cross realities, then yes; she can indeed fly away from reality.
I know it is nit picking, but I feel that it is important enough to do so. As I see it, it is more like because of Reimu can manipulate boundaries,
she is able to exit reality and attack from there.
It feels like sometimes all I see is a character and their abilities, instead of everything else. Look at Youmu, swordsmanship may be her
ability, but she is also very good at magic. Or Yuyuko, invoke death may be her ability, but she isn't a stage 6 boss because of that. She
is probably very good at fighting. This extends to all characters with vague abilities, it is not all they can do and some are shown, like Reimu.
In addition to flight, she can summon gods, weaken and strengthen barriers, warp space, do some boundary manipulation of some sort.
Yukari may also know how to summon gods, since she seems to know a whole lot about them and taught Reimu how to do it.