Lapis was finally free from everything. Tired of the Fighting, Tired of the Blame. That Mirror was a prison and fusion was the same. Lapis didn't have to be held back by the fears she went through trapped in the Mirror during the Gem War or her Toxic Relationship with Jasper fused as Malachite. She could enjoy her life on Earth with Peridot, The Crystal Gems and the Garden she grows. She's happy her life is happy.