This would be the same idea but with different words: "No estoy de humor. Quiero estar sola"

"To be in the mood" can be translated as "Estar de humor", "Tener ganas" or "Apetecer". "No quiero compañía, no estoy de humor", "No tengo ganas de compañía", "No me apetece estar con nadie" are some translations you can use.

One literal translate can be: "No estoy de humor, para compañia" But I think you can tell: "No estoy de humor para hablar". It's the same that tell in english: "I'm not in the mood to talk".