Mae'n well gen i goffi na te
Mae'n well ganddi hi goffi na the
Why is one te and the other the?
Both should say "the" in the context. Please report "Mae'n well gen i goffi na te" is you see it again :)
I believe the is incorrect. Te is the correct Welsh word for tea.
But does the na cause aspirate mutation?
Yes, you're right - my mistake, sorry.
Perhaps the problem is that traditional Welsh grammar requires aspirate mutation after "na" (= than), but many Welsh-speakers do not actually apply this mutation when a t or a p follow.
Oh, of course. Sorry, I forgot that, silly me ;-) Thanks for the reminder. I must say I have been a bit puzzled sometimes when there hasn't been an aspirate mutation, but I guess this course is trying to keep things simple.