But Linda clearly stated her reason. She said that she saw Banri as a bomb, and that if she told him the truth she would lose him again. Linda was not acting in order to treat Banri as a new person, or even in his best interest. She was pretending because it was easier for her and because of her fear.

Considering the old Banri and the new Banri as 2 different people only works if Banri is unaware of the old connection. In fact, he was getting along with Linda just fine until he saw the pictures. Whether he likes it or not, old Banri is still him, so are his relationships and deeds. From Banri's perspective, Linda was lying her socks off. Banri asked about her motive, and judging from his reaction, he certainly thought it was negative. You have to admit that it is certainly creepy for a close friend to pretend to be a stranger.

Also, Linda's actions cannot be said as actively trying to deal with just the current Banri. Her extra attention, kindness, the shoes, all those would not be there if they were not close friends before. She is doing all those either because of affection or guilt which should not exist if she really intends to treat the new Banri as a different person. Heck, Banri would probably be even less relevant than the senpais in the background.