If they were a het couple and this was just an underhanded tactic to spur interest in somebody they could just casually confess to, then yeah, I'd be with you.
But they're gay.
In China.
If Xiao Lu confesses, and Tongtong isn't interested, she might just turn her down and keep her mouth shut about it, but there is also a very real chance that she could go to her parents, or her teachers, either maliciously or just carelessly. Depending on the culture at her school and the opinions of the people in her life, she might get beaten and/or disowned by her parents. I don't think she can legally be expelled anymore, but rumors could spread, leading to bullying. Even if her parents mean well, she could still end up transferred to avoid discrimination and rumors following them. And it used to be way worse even than that. God knows what kinds of stories she's read or heard about people in her area from back before legal discrimination was repealed.
I will give a fair bit of leeway to any sexual minority who wants to use otherwise underhanded tactics to feel out somebody's interest indirectly before risking outing themselves. That shit is scary in a lot of places. The world may be growing up on the whole, but it isn't happening at the same speed everywhere. Some places are even backsliding.
(Edit: Just to be clear, I'm not saying there is an actual chance that Tongtong would do those things, she's obviously super into Xiao Lu and they are definitely on a romantic collision course. But Xiao Lu doesn't know that, so that stuff above is all reasonable to fear from her perspective.)
Yeah its honestly kinda wild to me that people have these expectations for Xiao Lu, especially considering the earlier chapter specifically showed us how she has this entire high-effort het disguise just so people dont get suspicious.
Not to mention that, although TongTong has obviously turned out to be a sweet and kind person, shed be confessing to someone who initially "blackmailed" her.
