Although I am not convinced that "Sinn Féin" means "Ourselves Alone". It is too short.
Surely, "Sinn" means "nous" and "Féin" means "mêmes", so that "Sinn Féin" means "nous-mêmes", "ourselves", written as two words in many languages?
But be that as it may.
Once Sinn Féin enters government, then it will never again allow any government without Sinn Féin in it.
That is the whole point of the present governing structures of Northern Ireland, on the principle that the alternative not only would be a lot worse, but was a lot worse, and was so for a very long time.
The governing structures are not, however, set up on any such principle in the Irish Republic, where people need to take note.
Once you have Sinn Féin, then you will never, ever, ever get rid of Sinn Féin.
You just need to know.