@cen3petal Correct! If you want to express in a formal way, you have to use the capital letter (singular), "Sua", "Le", "La", (plural) "Vostra", "Vostri", "Vostre", "Vi", "Loro", and even more. It doesn't matter the gender here, we're talking about a person or people... obviously not "Tua", because "tua" is informal.
Careful, we capitalize the first letter to distinguish between formal you and she, for several reasons: Accademia della Crusca supports this, most people who teach Italian use this method, and a number of users only began to learn Italian here (with plenty of sentences out of context) so using "lei" for both "she" and "you" would be a pretty wild way to start out! If you see "lei" or "suo" in the middle of a sentence, it is only accepted as "she" or 3rd person possessive. But if it "Lei" or "Suo" is capitalized, feel free to translate it with the formal you/your/yours!
For real life use, though - how do you communicate that the pasta on the plate is hers, not his? At that point in an actual conversation do you simply use someone's actual name? Learning so I don't sound like a complete entitled jerk when we go to Italy, but not at the point of using Italian in conversation yet.