Informal and playful:
* E aí, gata! (Hey, girl!) - This is the most common and straightforward way to say it.
* Oi, linda! (Hi, beautiful!) - This is a bit more flirty than "E aí, gata!".
* Oi, gata! (Hi, girl!) - This is a less playful version of "E aí, gata!".
More formal or respectful:
* Olá, moça. (Hello, miss) - This is more polite and suitable for a more formal situation.
Important note: The best way to say "Hey girl" in Portuguese depends on the specific situation and your relationship with the person you're talking to. Using the informal options with someone you don't know well can be inappropriate.