They decided to squash the beef and be friends again.
squash the beef
idiomTo resolve a grudge.
Origin
disputed originBeef here is used in its sense of "grudge", "dispute".
After arguing for months about the project, the two coworkers finally sat down to squash the beef.
Despite their long-standing rivalry, the two leaders eventually agreed to squash the beef in order to focus on the common goals of their organizations.