[So if , in English, we had BLACK, then you might get WHITE ( opposite) or MAGIC (complement) etc ]
Here's a simple example .. suppose the words I gave you were ...
gwg wyres uffern
so the opposites would be ......................
gwên ŵyr nen
and the thing that frightened her would be " gŵn " ... a gun ( not a gnu, obviously).
Right ..here we go with the real one you can have a go at .... here's your words ... you're still trying to find out what's scared her ...
llefain caws celyn pili-pala colled soddi
One of the neat things about this type of puzzle is that often you might have a choice of words, and you need to pick the one that leads to a sensible answer... that way you're encountering a greater variety of words and using your brain a bit more. Plus, if you get most of the letters, you can usually work out what the rest need to be.
After all that, here's the excellent Yws Gwynedd with his one-time Christmas Single " Fy Nghariad Gwyn" ...