No..it's actually her fault..,but she has done that..she has eaten Annie..

This mission here... Eren was supposed to be the one who ate Annie to get more information about Titan, but when he was on the verge of the mission Eren stopped... and there Annie almost became a crystal she closed her eyes and her body formed a crystal stone. However, before Annie had time to completely become a crystal, another female Titan came from another direction, kicking Eren who was still in Titan form until Eren fell to the ground. Nia in Titan form immediately directed her lips towards Annie's crystal until finally it shattered in her mouth and Annie was declared dead right then and there, Nia now has two female Titans in her body. Armin and the entire scout team were shocked to see this unplanned incident, Nia did this not on purpose... this had an element of revenge. Several months after the incident, Armin accompanied Nia more often, he knew this was hard for her.

"Are you...feeling better?" Armin glanced slightly at Nia, hoping she would answer calmly.