・・・。
Childhood friends are scary...
Literal
Childhood-friend [topic-って] scar-...
Ultra-casual sentence fragment. 幼馴染 'childhood friend' is a productive cultural term in Japanese, often loaded with romantic/nostalgic connotations in anime and manga. って is the casual topic marker. こわ is a clipped/cut-off form of 怖い 'scary' — the ellipsis after it suggests the speaker is trailing off rather than finishing the thought. Blog/chat register.