I get confused about mutations following y/yr. Is it feminine nouns that have a soft mutation?
The 'ap geiriaduron' free dictionary for smartphones is great for this.
Beth sy'r broblem? :(
You wouldn't use 'sy' here. You would use either 'ydy' (North Wales and standard) or 'yw' (South Wales).
'Sy' is the relative pronoun and means 'which is/are'.
You missed my making fun of myself - we do that in our culture. Maybe my Welsh was not good. I was trying to say, "Is it Beth who is the problem?" Maybe! :)