Alice lived in the same part of the wall as Eren and she was best friends with Eren and Mikasa and Armin. She knew that Mikasa had a lesbian crush on her but she was actually in love with Eren. However, Alice realized that she actually likes Mikasa a lot and that she wanted to have a threesome with Mikasa and Eren. She hated Armin. So, from that day forward she embarked on a quest to have a threesome and get Armin killed. That day was also the day the titans scaled the wall.
The four of them took on the training thing together and became trainees. Alice was even more talented than Mikasa and on her first day at the training boot camp she was offered to become head of the military police. She rejected them because she wanted to be with Eren. Alice was also prettier and Mikasa and was full Japanese cause her family were from Japan and more racist. They never married any foreigners ever.
On the day the titans attacked again Alice's love allowed her to see that Eren was the giant titan. She told Mikasa and Armin. She was really disappointed Armin wasn't eaten. She hated him, he was really whiny and weak. Together the four of them stood before the humans who were planning to kill Eren. Alice and Mikasa stood in front of Eren and Armin. They were about to scale the wall when Eren turned into a titan. Alice was happy, because she was finally inside of Eren with Mikasa. It was too bad Armin was there.