Such as all the costume changes for Beyonce in a concert...
Bro, we think of fantasy as "not reality" or an illusion someone imagines, not unusual clothing. For unusual clothing we could say costume (pretending clothing) regalia (special clothes for something like a ceremony) or uniform (clothing specific to a job, school, military, or an organization)
In English 'fantasy' can be anything that is not based on real life. A fantasy costume. A fantasy book. A fantasy game.
I think [but really... I'm not a Brazilian genius] that costume is intended as masquerade...
She is wearing a costume =
- Ela está a vestir uma fantasia (EU PT)
- Ela está vestindo uma fantasia (BR PT)
So does 'Ela veste uma fantasia' mean that she (usually/normally) wears a costume, rather than that she is wearing one now?
She wears a costume... to the ball.
She wears a costume... at work.
What does she do for her job at Disneyland? She wears a costume.
This exercise is a "Simple Present" one not a "Present Continuous" one.