I also like the idea that Peig only speaks Irish, but that all the other characters can understand her without a problem.  In reality, only Synge and perhaps Lady Gregory would be able to converse with her.  Even though I have an avatar of myself in there (helping Yeats and Joyce at the doctor’s office in the last panel) à la Alfred Hitchcock and M. Night Shyamalan, she wouldn’t even have been able to talk to the other villagers.  Gaelic (properly called “Irish” or “Gaeilge”…but I use “Gaelic” here for ease of understanding for the general public) had already long died out as a community language in Tipperary by the 1930s.