Green’s Dictionary of Slang

(US) jealous.

1915		T. McNamara Us Boys 15 Feb. [synd. cartoon strip] Naw; he couldn’t be jelly! How could he be jelly at a poor boob like me?
1931		C. Martinez ‘Gats in the Hat’ in Gun Molls Sept. 🌐 ‘You’re just jelly.’ ‘Yes, I’m jealous,’ she admitted. ‘I don’t like it when you have your arms around that snaky dame.’.
2012		C. Eble (ed.) UNC-CH Campus Sl. 2011.
2016		C. Eble UNC-CH Campus Sl. Spring 2016.