Context: She was waiting in the snow for someone and after she met him and after they had gone inside and she had touched his face with her hands he said "バカ、こんなに冷たくなるまで俺のこと待っていたなんて. She then whispers "冷たいのは違う”(as indicated by the ぽそ sound effect) before she responds. The reader knows that she is a 雪女(whilst he doesn't) so it would make sense for her to be 冷たい, but my problem is with grasping what she meant by that. I think this might be her saying that, that(referring to her standing out in the snow all this time) is not why she is 冷たい although I am not quite sure.
3 Answers
I think that you are reading between the lines "correctly". Unless the larger context proves otherwise, what you stated would be the most natural and logical way of understanding the phrase 「冷{つめ}たいのは違{ちが}う」.
It would mean something like "Me being cold has nothing to do with it." with "it" referring to the fact that she had waited (outside?) so long on a cold day.
Since this line is not one she, as a snow fairy, wanted to say assertively and clearly, she said it 「ぼそっと」= "murmured it".
I think that maybe because she's a 雪女 she doesn't think that's actually cold, so the translation for that sentence could be "it's not that cold!"
「冷たいのは違う」simply means that you're wrong to say that I become cold, or something close to that. I guess she wants to emphasis on the things that she've been waiting for him for long, but couldn't say obviously. That's why the expression,「ぽそ」comes later. She could,ve simply said that '冷たくない', which also means that I don't feel cold. But, it seems a little direct and straightforward to say, so in this case 「冷たいのは違う」might sound better.
