@Krune
Kaname heard her voicemail in last chapter, so at least she knows that she was supposed to go.
So yeah, probably it was her plan all along. Predicting that Piyo would take Tsubaki on a pseudo-date if she didn't appear.
Remember she's also the one that gave Tsubaki's number to Piyo in the first place. She might be playing matchmaker, the real problem is that we don't know her reasons. Kaname is kinda hard to read.