Hi Nadiawitczak,
Thank you for using the Apple Support Communities. We see you want to know if you can leave a Group FaceTime call, and we're happy to share some information about this.
This resource covers how to Use Group FaceTime on your iPhone, iPad, and iPod touch and provides the details below:
"When someone is added to a Group FaceTime call, they can't be removed from the call. The person who was added to the call needs to end the Group FaceTime call."
The initiator of the call would need to end it using the steps in the "Leave a Group FaceTime call" section of this link: Make a Group FaceTime call on iPhone. If you'd like, you can send your suggestion to Apple using this link: Product Feedback
Take care.