Yes, she can always comeback to Cherry Bullet, but she just adds so much to the show that without her vocals and kind nature I'm going to feel really empty, especially now that we are having the original songs ( she fits utopia sooo much ,dayum!).
I read a comment on Reddit that said that she really wants to continue on the show and debut on the final line-up, she really wants to stay and receive votes... And I can understand, she might see this as a better opportunity for recognition than just being in cherry bullet.