I think this means - as they say - but I'm not quite sure - 'sé sin le rá' - and what is the full spelling of 'sé ? Here's the complete sentence -
Bhí Gráinne 'millte' - 'sé sin le rá, bhí sí ina peata críochnaithe.

I think I'd translate that as "that is to say." For "as they say" I'd lean toward "mar a deirtear."

Redwolf

Agreed and 'sé sin le rá is a contraction of is é sin le rá.

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Múinteoir Gaeilge - Irish Teacher
My "specialty" is Connemara Irish, particularly Cois Fhairrge dialect, but I can also speak Ulster and Munster Irish with native-level pronunciation.
Is fearr Gaeilge ḃriste ná Béarla cliste, cinnte, aċ i ḃfad níos fearr aríst í Gaeilge ḃinn ḃeo na nGaeltaċtaí.
Gaeilge Chonnacht (GC), go háraid Gaeilge Chois Fhairrge (GCF), Gaeilic Uladh (GU), Gaelainn na Mumhan (GM), agus Gaeilge an Chaighdeáin Oifigiúil (CO).

Ceart go leor - (it's because they keep missing out letters like that, that I can't understand it)GRMA