Board Thread:General Discussion/@comment-26293010-20150703035403/@comment-28584561-20150703112458

Pearl has no qualms fusing with Garnet. From Coach Steven:

Pearl: WAIT! Garnet, think about this. You and Amethyst can be a bit... eheh...unstable when your personalities combine. We need to be careful! Fuse with me, instead.

Garnet: We don't need to be careful. We just need to be huge.

Also, when they fuse succesfully, no one personality is dominant than the other. All the individual personalities are gone and leaves behind a single unique personality that embodies the individual personalities. Only when the synchronization of each Gem falters will their indv. personalities become apparent.