I guess right now, Yuki is too hurt by the betrayal of her mother reminding her that people throughout her childhood never gave her the love she needed. The people around her are also broken in different ways and can't really give her what she wants, and she's too fearful of another betrayal to trust others enough to open up herself.
I relate to her a bit in this chapter; particularly the part of being lonely but terrified of other people. Unfortunately, unless you do it scared, you won't make progress. Taiyou is not the right person for this in the end, but I hope in future chapters, Yuki will meet someone who can make her open up. Or even better, please get therapy 😭