Learn Portuguese (Portugal): A rapariga arranhou-se na perna e no braço.

Arranhar means "to scratch". By adding the reflexive pronoun -se, it literally becomes "to scratch oneself". In Portuguese, instead of saying she scratched her leg, it is more natural to say she scratched herself on the leg. Arranhou is the simple past (Pretérito Perfeito Simples) for "she".

Why is the -se attached to the end of arranhou with a hyphen?

In European Portuguese, pronouns like -se usually attach to the end of the verb with a hyphen in basic affirmative sentences. If the sentence were negative, a word like não would pull the pronoun to the front (e.g., não se arranhou).

Where is the word for "her" in na perna e no braço?

Portuguese rarely uses possessive pronouns (like "her" or "his") for body parts. Because the reflexive verb (arranhou-se) already shows that she did the scratching to herself, it's obvious whose leg and arm are involved. We just use "the" instead of "her".

Why do we use na and no before the body parts?