Selene is absolutely incompatible with the Great Thirsty. She's lustful, but only casually. She's lethal, but not bloodthirsty. She's also an odd mix of prideful (don't call her stupid) and indifferent to pride (doesn't really care about being best at anything as long as she's not the worst).
Selene is the closest thing there is to an Eldarii Living Buddha. Selene is 99% satisfied just being herself and that's utterly the wrong thing for The Great Thirsty's avatar.
Either that or she's something like an Untouchable in that Warp energy doesn't effect her. She did get sucked in by daemons and came out much later no worse for the experience.