Learn Italian: Mia madre sa cantare bene.

In Italian, when "can" means "to know how to do something" (like a learned skill), you use the verb sapere (to know). The verb potere is used for physical ability or having permission. Since singing well is a skill she learned, Italian uses sa (she knows how).

Why is it just mia madre and not la mia madre?

Usually, possessive words in Italian need "the" in front of them (like il mio gatto for "my cat"). However, there is a big exception: singular, close family members do not take the definite article. For "my mother", you must drop the la and just say mia madre.

Why is the verb cantare not conjugated?

When you have two verbs right next to each other describing a single action (like "knows how to sing"), only the first verb changes to match the subject. Here, sapere becomes sa for "she knows how". The second verb stays in its infinitive (dictionary) form, which is cantare (to sing).

What is the dictionary form of sa?

It is sapere (to know). It is an irregular verb, which is why the "she" form (lei sa) looks so different from the infinitive.