Sayu fucked up an said some shit publicly that was supposed to remain private so Matara felt betrayed by someone she considered a friend and went no contact. Understandably she has no desire to be in the same company as her but seeing as Zen and Sayu collab'd and Matara clearly doesn't mind (it's not like she suddenly stopped playing with Zen) she's not being vindictive or anything. There's really not a lot of drama here.