'Gagged' in current Gen Z slang means shocked, stunned or speechless in the best possible way — usually because something is so impressive, unexpected or funny that you have lost the power of speech. 'I am gagged' = 'I am floored'. The term comes from American drag culture (RuPaul's Drag Race popularised it in the 2010s). It has no violent or sexual connotation in this usage. If your teen says a performance, outfit or post 'gagged them', they were impressed. Tone is admiring or amused.