What is rizzing up a girl?

I'm curious, could you elaborate on the term "rizzing up a girl"? Is it a slang term for charming or attracting someone romantically? Or perhaps it's a phrase used in a specific context or community? It seems quite unusual, and I'm eager to understand its meaning and potential nuances. Is it something related to online dating, flirting, or something entirely different? I'd appreciate your clarification.