to make it quite simple, "별로 + negative adj" has the same meaning as in "not really + adj" in English 별로 안 춥네 - it's not really cold 영화 어땠어? - how was the movie? 별로 안 무서웠어 - it wasn't that scary

Same thing the difference is like this:

Im not attracted to him

Im not really attracted to him (im not particularly attracted to him; im not especially attracted to him

A: 넌 이거 어때? 이뻐? What do you think of this? Is it pretty?

B: 별로야 Its not all that great; its not particularly that good;

A: 오빠 그 여자가 좋아 Oppa, do you like that girl?

B: 아니 그녀는 별로야 No, shes not that great; shes nothing special

A: 오늘 바빠? Are you busy today ?

B: 뭐, 별로 할 일이 없어 Well i dont have have anything to do in particular

감사합니다 :)

Slight differences between them. 마음에 안 들어요. = I don't like it. It sounds more determined. 마음에 별로 안 들어요. = I don't like it much. It sounds more a step back than the fist one 별로 means not much So, 별로 is usually used in a negative sentence and can be replaced by 그다지