Hi Laura, 왜 이렇게 좋아하는 거야? = 1) why do u like it/him/her/them/me so much? 2) Why are you so happy? (Sometimes it is used when asking why someone is laughing.) Ex. A: 휴.. 걔가 너무 좋아서 미칠거 같아 (phew.. I'm almost going crazying because I like him so much). B: 왜 이렇게 좋아해? (why do u like him so much?) A: (laughing) bahahahah B: why are you so happy? Hope it helps.

I think.... that means "What's so funny?"