Alisha's rented room was cramped, so he rented her a two-bedroom apartment, and it naturally led to Harry/Harriet spending all day with her, and he also started coming over to stay every night.
Alisha didn't know when she started getting used to Tyson Thornton's return home, began to feel accustomed to having something of his in the house, in short, she unwittingly started to think of Harry/Harriet as her own son, and Tyson Thornton as an indispensable part of the household.
The real and complete transformation of her relationship with Tyson Thornton was catalyzed by another visit from Oliver Johnson.
That time, Oliver Johnson insisted on having a serious talk with her, and by the end of it, both were in great pain. Oliver begged for her forgiveness, asking for another chance, promising that he would never betray her again.