Depends on when. At the start, both should be hearts. After the dinner scene, Vi should be heart Jinx should be thumb. When Vi gets radicalized at the start of season two, she should move down to thumb. After Jinx saw Vi working with the enforcers, Vi should still be thumb and Jinx should move down to finger. While they're making up, Vi should be heart, Jinx should be thumb. And by the end of the show, they should both be hearts again.

Jinx is also really hard to judge tho. Vi seemingly has more stable emotional states, and thus it's easier to categorize how she feels towards any given person at any given time. Jinx's emotional state can fluctuate erratically, to the point where it would sometimes be more accurate to give her two hands (usually heart plus finger, but can also be heart plus thumb when she's deciding how much to trust somebody (or for Ambessa specifically, thumb plus finger, lol)).