I've heard in a song the following line:
すれ違い心見えたなら 「要らない，要らない」しないのに 貴方はいつも貴方のまま
This seems to mean something like "If I met someone whose feelings differed from mine, I wouldn't say 'I don't need it, I don't need it", but you are like you have always been". I have no confidence at all in this translation and I would appreciate it if someone came up with a better one. I also would like to know why it's 見えたなら and not 見えたのなら.
Anyways, it seems that すれ違い means something like "to differ" or "to go against". However, I looked up at some dictionaries and it seems that すれ違う means almost the same as 外れる and ずれる. Are there any differences? Moreover, what is the kanji for すれ違い's すれ?