Hah! I totally called that shit.
As to her motives... we have almost nothing to go on regarding her motives. We lack too much info at this point to . All we know for sure is this:
- Annie is confirmed to be the female titan.
- She went to capture Eren even if she had to slaughter half of the expeditionary forces to do so.
- She was hesitant to kill her former friends/comrades from boot camp.
- She killed the titans who were captured during the battle at Trost.
- She took Marco's 3DMG from his dead body after the battle to avoid having her own gear be inspected and thus exposing the fact that it had been used very recently.
I think that Annie hates the fact that she can turn into a titan. She seems to be lamenting a lot of the time, like when she said her father forced her to learn his style of hand-to-hand combat. I feel that she wants to live a life in obscurity - to not stand out, to be "normal", since being able to transform into a titan is a rather large Red Flag. Thus she always seems to do things half-assed, never gets excited about anything, doesn't like to have people pay attention to her. This probably goes against her true self, so she can't always resist people like Eren who tries to live true to himself and does what he believes in, nor can she not stick out much of the time because she tries too hard not to be noticed. Because she resents her titan powers she suppresses her urge to be a part of of the group, or to be too friendly with others. She has accepted her fate as someone who can use titan powers and all that entails, but it's definitely something that was forced on her. I smell a flashback coming on!
Even though I believe guessing is mostly futile at this point, I'm gonna give it a go anyways.
First off, Annie was under orders. The chances of her acting entirely alone are practically zero. She is almost certainly involved with a group of people who can turn into titans like Eran(e.g. the Colossal Titan and the Armored Titan).
Secondly, I believe their are 2 possibilities as to why Annie was picked to go after Eren and not another titan. The first is that she was selected as the best or most fitting for the task of retrieving Eren. This could be due to any number of factors such as her specific abilities as a titan, her being the only one of them who knows what he looks like, etc. etc. The second possibility is that this mission was a test for Annie. Perhaps a rite of passage or something similar. By completing this mission, she would be initiated formally into their little group. What she says here lead me to think of this possibility.
Based on some more comments on the pages before this one I think it's probably safe to say that the human-titans are using the underground city as a hideout or base of operations. Since she failed her "initiation" mission, she is not allowed into their main base, thus possibly explaining the reason she cannot go with them. She does not want for them to go there either(as it's probably suicide) but she can't tell them why without admitting she is one of them or giving away the location of their base.
I also believe that ring she has is important as well. It may allow her to keep herself fully lucid when she transforms. There are some other possibilities as well. Then again, it may do nothing at all and just be some sentimental item. I'll bet you all ten bucks that we'll be able to figure out what it does(if anything) in the next chapter.
That's about as much as I can theorize. Anything other than that is a 100% stab in the dark.
Sorry for the wall o' text. I'm sure most people won't bother reading it, but i felt like getting it out there regardless.
To those of you who DID read it, what do you think?