Are we still catholic if we no longer practice the beliefs or the catholic church?

I was told by someone that we are not. Cant remember who it was or whether they were a priest or not.

I mean if a person is baptized in the Catholic church then they are said to be catholic.
But i was told by someone that if they do not actively practice or even believe in the teachings of the Catholic church then they are no longer Catholic.

Its like i know a couple of my friends, who are Catholic, they call themselves Catholic, they go to mass occasionally but then they have sex outside of marriage and actually promote it too. But they still consider themselves Catholic and don't see whats wrong with it.

I also have a friend who considers herself Catholic/Hindu, and prays to both. But that conflicts with the first commandment.

And i have another friend who calls herself Catholic, but she says she doesn't believe in the trinity. She says she doesn't believe that Jesus is one of the three persons of God, she just believes in one God. And she also doesn't believe in the immaculate conception.

All of them were baptized Catholic. Are they really still Catholic?