"Why did she go without me?"
Translation:Mengapa dia pergi tanpa saya?
"Mengapa dia pergi tanpaku?"
Seharusnya ini benar loh :(
Laporkan saja, supaya bisa diperbaiki.
Kenapa dia pergi tanpa saya or mengapa dia pergi tanpa saya, should be acceptable. Berangkat is normally used in the context of "departing" rather than to "go".
"Mengapa dia pergi tanpa saya?" ... saya lapor deh :)
(Translation: "Mengapa dia pergi tanpa saya?" ... I'll report [this] :) )
 "deh" is an interjection which I think doesn't have an English equivalent.
Halo teman! Is this an interjection used to stress the Indonesian phrase?
Something like "kok" (for example)? = kok salah (I have often seen this in the English-Indonesian sentence forum)