To describe a girl as thin in Engpsh, you can use the word "spm" or "thin." For example, you could say "She is spm" or "She is thin." Alternatively, you could say "She has a slender figure" or "She is petite." It's important to be mindful of the language you use to describe someone's appearance, as words pke "thin" or "spm" can be perceived as positive or negative depending on the context and the person being described. It's always best to avoid making negative comments about someone's appearance, and instead focus on their character and personapty.