
This is the scene where Dina was injected the titan serum...
http://www.mangago.zone/read-manga/shingeki_no_kyojin/mr/shingeki-no-kyojin/87/pg-21/
Her transformation...
http://www.mangago.zone/read-manga/shingeki_no_kyojin/mr/shingeki-no-kyojin/87/pg-23/
And Eren confirmed it by himself that Dina ate her mom
http://www.mangago.zone/read-manga/shingeki_no_kyojin/mr/shingeki-no-kyojin/87/pg-27/
http://www.mangago.zone/read-manga/shingeki_no_kyojin/mr/shingeki-no-kyojin/87/pg-28/

I see. Maybe because Annie's titan more feminine vibe than Dina's or something like that... XD My theory is Annie is conscious what she's doing prior as she's supposedly to be a well-trained spy while Dina and others (rebels-turned-titan) roaming around outside the wall, looking for food...humans to chew
When i saw Dina in her titan form, i was shocked that i evern didnt get noticed im shedding tears. Her last words were like giving prophecy that she will meet grisha again but damn dina y did u eat eren's mother? Σ(っ°Д °;) btw the resemblance of the owl's titan form to eren was more shocking... ugh sensei ur so good at twisting and pulling plots. Hats down