>>535773139
The Melt treatment worked because it involved a time-travel twist. And because she met Guda at the lowest point of her life. She suffered miserable endings in all the EXTRA storylines she participated in, so meeting a human who treated her nicely and trusted her, despite being an AI, was a welcome change of pace for her. Not to mention it was the first of its kind in FGO, before "I secretly saw Guda's simulations/adventures, so now I love him" became as lazy and cliché as "I fell for Shirou because he tried to jump over and over."

It's kinda like how Shiki fell for Kokuto. Dangerous, rude, and cold girl has her frozen heart melted by a naive, optimistic, and gentle boy.