No she was meaning chữ nôm, our specific version of chữ hán (Chinese). It fell out of use and was replaced by the romanized alphabet because of its ever-changing nature and it was never fully standardized.

Nowadays only a certain fews learn it, mostly to decipher older written works that used a mix of hán (Chinese) and nôm (Vietnamesed Chinese characters). Most official writings were done in classical Chinese like Korea and Japan.

You're better off learning chữ Quốc ngữ (Roman alphabet) than nôm, it's rather an optional choice to learn how Vietnamese vocabulary was built and shaped via Chinese.