User blog comment:San&Ashitaka/Chapter 51- Expectations/@comment-96.49.50.134-20131101013306/@comment-179280-20131102033734

I don't know why people think EreMika is non-shippable and throw in the argument that "they are siblings". That's just nonsensical. Yes, dating your own brother/sister would be weird, but they aren't actual siblings, and Eren has told her just that a couple times (chapter 11 and episode 11). Besides, it's pretty clear she sees him as something else than her brother (chapters 13, 34 and 50), even though she denies it.

While I don't ship EreMika, you have to admit Isayama has left it pretty clear that she has feelings for him (and yes, canonically one-sided relationship).