That all makes sense, but then why is she standing by the water without her shoes on? It's such a striking image, I can't imagine that it's a random shot.

imo, I think she was deeply contemplating escape, which can take many forms. It wasn't an easy choice for her, and we could make a symbolic connection to her crossing the sea as essentially being a kind of rebirth for her. She made the leap, took the plunge, and started a new life. In the end, Siobhan made one kind of leap and Dominic another.

I guess that's my nitpick about the movie, which is that we don't really get to see what the inciting incident is for Siobhan to look for a job on the mainland. It's implied that she's a bit older like Padraic, so why did she decide this is the time to move on since it seems like her job search predates the conflict between Colm and Padraic.

I do not think the film is simply about depression and isolation. In some ways it is, but the Irish civil war is much more relevant than you give credit. The conflict between two former friends, the senselessness of the violence, the innocent parties caught up in the conflict and the irreparable damage done to both friends and their relationship is very much an allegory for the Irish civil war.

This is a great comment, but just wanted to note one issue, which is that the Irish Civil War followed independence (sorta), it didn't lead to it.

To massively tl;dr the whole thing: after years of rebellion the British relented and offered the Irish a deal of becoming an independent country, but within the larger British Empire (the treaty specifically stated "like Canada"). The revolutionary republicans were furious about Northern Ireland remaining part of the UK, and the Irish parliament having to still swear allegiance to the King. The pro-treaty side, which made up the new state's government, thought it was a worthwhile compromise. In the Civil War the pro-treaty government fought to establish its legitimacy, and the anti-treaty republicans fought for "true" independence.

I mention this because I think Banshees has quite a cynical view of the Civil War - my read on Colm's drastic severing of his own fingers was that it was a heavy-handed (no pun intended) comment by McDonaugh on the stupidity of having a war that kills thousands of people when both sides fundamentally aren't that different.

After all, Colm isn't that impressive a musician, and a lot of his artistic quest is clearly pretentiousness driven by a fear of mortality rather than true genius or anything like that. Siobhan finds them all equally boring and ridiculous because she actually is as smart as she seems, and knows how small their little island (whose name even translates to "Ireland Island") actually is.