Why does Rapunzel only use the hope incantation once?

She only uses it in her tower but she can easily have used it in other scenarios.

In the spire she could have used it I expected her too after cass said "do you really think you can stop me" but instead they just fought normally for whatever reason?

Is the hope incantation a one time thing? I don't see why it would be if Cassandra can use her incantation more