Hi Nube Pequeña.
The Spanish language varies from country to country where it is spoken. Not only the accent, also the vocabulary, pronuntiation, grammar and meaning of the same words vary. The only thing that doesn't vary is the orthoraphy, regardeless the pronuntiation, the words are spelt the same in every Spanish speaker country.
There are a lot of examples in the forum, one of them is amo/me encanta. In Spain and Peru, me encanta, in Mexico, amo.
Ahora, referente a tu pregunta, tú lleva tilde cuando es pronombre : tú eres italiana, you are Italian, y no lleva cuando es posesivo: tu idioma materno es el italiano, your mother tongue is Italian.
Lo mismo con mí/mi.