Thanks all...
The yellow guy is gone...
I turned on the lights today... the trigger was in her normal spot, so I thought nothing had changed over night anyway...
Instead to my suprise the Undy turned around and swam around in the cave, then showing me she is okay she took a bite at the rock...
The tail still concerns me, however I think as another poster had said... I think I made her socially inept, the the yellow damsel freaked her out.
Just very glad that the story is still possitive...