Well this is an interesting read
Contrary to the comments above i like to think that it's not yukari and ran that abandoned chen you know
My thinking was when yukari "disappeared/died" ran who is the older one goes on a rampage and leaves or just can't cope with yukari "death" and try to search for yukari
As for chen she is the younger one and maybe quite helpless so she can only wait for her master to return
At least that's my best attempt to make sense