Is it worth it to Train Rozalin and Tink in Disagea Dark Hero days 2?

Well ive been playing and im in chapter 5 or 6 wherre the colessum is and iall my characters are like lvl 40-100 and i do not know if i should train Rozalin and Tink becuz if they betray me imma have to put up a fight soo should i train her???