Omake ScreenCap - Fairy Tail Final Season - Episode 313 - Erza Ready for Battle

Erza listened to Irene's personal history and immediately donned a bunny girl suit of armor. She's just awesome like that.

Irene explained how she used her enchantment magic to create the first generation of Dragon Slayers, herself being the first one. Unfortunately, she suffered the same fate as Acnologia in becoming a dragon, but it was Zeref who returned her to a human form. However, she wasn't a human; she was only a dragon who could look like a human. She abandoned her daughter Erza when her attempt at using her body to become human again failed. And that's why Erza just wants to fight and stop her mouth from making more noise.