I read this not-actually-all-that-bad science fiction novel a few years ago about a woman on a colony planet that had been taken over by Evil Aliens who had this ability. She could feel her twin's pain. In fact, her twin didn't feel any pain at all because the woman could feel it (or something like that, it turned out the twin was the 'stronger personality' and kept shoving her pain off onto her twin. Nice). Anyways, the stronger twin was spying against the Evil Aliens and got caught, so they tortured her to death. Naturally she didn't feel any pain from the torture because she shoved it off onto her twin. The physical damage to her body finally did her in. When the book opens her twin is still recovering from the after effects.

And then the surviving twin met a member of the feline Good Alien race and feel in psychic love and annoyed me to near death with her TSTL behavior. So I quit reading the series.