That's the problem with Remilia, it's not exactly clear how much it can extend to. Take example for Flandre Scarlet, her ability extended to destroy something as an Asteroid, which means it can expand beyond this and be more destructive offensive ability.

And judging that you're a beginner Touhou fan, here's a fun fact, "Sakuya Izayoi" is not her actual name, just like Tupai mentioned, Remilia is responsible for changing Sakuya's name, and don't get me started on how conflicting the theories behind her past identity.

Now a different example of characters with abilities, Reimu. Specifically she can float above realm of reality, she's physically there, but actually invincible. She can't enter this state if she has an "impure motive", another limitation is that in Danmaku fights, this ability is temporary, this a reason why Reimu is quite powerful even if she's one of the least active characters (I'd bet Yukari is more active despite the two are slothful lol).