It's not that she is afraid of tainting pure gems, it's that she doesn't want them tainting her. If that doesn't make sense, let me explain it like this. She knows she's not a real gem, (made of old car paint) and wants to prove that she can be just as good as a real gem. So she will go to great lengths to do so at times. It would take some convincing or a situation where there was no other choice in order to get her to fuse. Let's see, in a fusion, depending on who fordite fused with, her swordsmanship would either be more defensive or offensive. In the case of Bix, it would add some extra oomph to her shield, like maybe a deflective shield, or countering shield. I could also see palette swap being very useful here, especially since she's a gemgineer. imagine needing to do quick repairs that can't be done by yourself, BOOM several more (fusion name here) to get the job done Zirnconia is a little harder, perhaps adding differently colored sword bits to the drill hammer, turning it into a slaughter machine. The two of them might go well together personality wise, or since they are so similar personality wise they may not last long when fused, but perhaps their nee to seek approval or prove themselves might make them a strong fusion to contend with For Nephrite I see the two of them fusing well on the weapon front, Palette swap plus Telekinesis makes for an awesome homing rain of death arrows.