I agree with what people have been saying here, but I don't think that means Peridot lost interest in fusing. What she said is "I had hoped to gain a better understanding of fusion. Instead, I gained a better understanding of Garnet." She never specifically said that she wanted to understand a fusion like Garnet, just that she wanted to understand fusion in general. She might still be interested in fusion.
Yeah, exactly. She just wanted to understand fusion in general. So, she might be still interested in fusion. She might not be ready to fuse yet but, she might want to fuse eventually.
What if she never does? What if know your fusion is about Steven as maybe he finds a way to fuse with a gem.