Questions & Answers about Mia sorella è molto competitiva.
With a singular family member in Italian, you normally use the possessive without the article:
- mia sorella = my sister
- mio fratello = my brother
- mia madre = my mother
So Mia sorella is the standard form here.
You may see the article in some cases, for example:
- with plural family members: le mie sorelle
- with a modified family noun: la mia sorella maggiore
- in some regional, older, or emphatic usage
But in a simple sentence like this, mia sorella is exactly what you would expect.