"Yo" question

[Liquinn3]

Hi, I'm speaking to a girl that's native language is Spanish on Twitter, she's said "Yo vivo en" and "Yo tengo".

I thought the "Yo" wasn't needed, could someone confirm?

[AngelicaDeAlquezar]

The fact that it isn't needed doesn't mean it's forbidden to use.
Pronoun usage depends on issues related with emphasis, clarity, disambiguation...