Hm. I would have to say out of the choices you gave us from the Crystal Gems after reading her backstory,I would have to choose Garnet. ^^. I figured she would best suit her. Not because their both fire types,but how they both seem to be quiet and distance,along with how Homeworld treated both of them.
I believe they would make a stable fusion,that's quiet and would only fuse when necessarily needed. Although that's just me talking with small suggestions. ^^'. In the end. It's really up to you with on who you want to fuse with,as I'll be looking forward in seeing the fusion result <3. ~Ozzinq♥.