It's definitely as the above commenter said: Leon's being super passive, which seems to be nice in theory, but it's not as nice in real life. When someone just lets you do whatever you want and doesn't make any moves of their own, it feels as if they don't want to spend time with you at all — like they're just indulging you and spending time with you because YOU want it, not because the other person wants it, too. Relationships are a two-way street, so he should also be vocalizing his wants and feelings. Just like Leon can't understand her unless she explains why she's upset, she can't be sure about what Leon feels unless he shows it to her or talks about it with her.
Why is Lizzie feeling vexed? I didn't get it