Tua is part not commonly used in Brazil, right? And how do you know when to use teu/tua? Is the gender based on the noun attached to it (salada is feminine, so they used tua) or is it based on the person you are saying it to? (Ex. if this is being said to a man, would you say "Come a teu salada"?
I think this is only true with the verb "ser" (to be), and only when identifying something or someone, like the sentence "It's a woman" does. When you say "It eats your salad", "it" is a pronoun for an animal or object (i.e. something eats your salad), and this always translates to "Ele" or "Ela".