Let them leave because Yun Ran has already outsmarted them once. They didn't die, which means their fate isn't over yet.
Xuanmen people, even if they're highly skilled, must respect fate. Unless it's a matter of life and death, it's best not to go against the heavens.
Secondly, she's also injured now, and these four old folks certainly have backup measures. Trying to eliminate them would come at a painful cost.
If the elders of Qingfeng Temple, especially her little uncle, knew she almost played herself into danger just to eliminate a few morally ambiguous old monsters...
She'd be hanging for three days and nights and be scorned from head to toe.
She can even predict what her little uncle would say: Don't ever say you grew up following behind me; I'm afraid others will mock me for raising a fool!
The powerful evil cultivators killed by her little uncle were rarely taken down one-for-one; most were tricked to death.
