Sorry for the confusion. The following is written under severe influence of NyQuil.
I have had Irish citizenship for well over a quarter of a century, so it wasn't obtained solely to get the Daughter into the UK or any other EU country. At one point in the 1990s I had wanted to move to Ireland and did extensive (and expensive legal) investigations of the logistics. I could not move us there when the Daughter was a minor due to California custody laws, even though we (and the courts) couldn't locate the absent parent for the necessary permissions. Bottom line, if we could have moved over before she was of legal age, or after, we'd not be having this conversation. She and I would be Irish citizens and there would be nothing to discuss here.
But for the now, unless the EU goes completely anti-immigrant, if the Daughter is tossed out of the UK after Brexit we'd probably both go to the Netherlands, or potentially to the north of France. Both appear willing to allow her in as my dependent/family member. While I can go to Ireland to live, at present she cannot - unless we can get citizenship for her, which would be hella-tricky to do since they don't normally recognize adult dependent children, although it's not completely out of the question. (Things seem to have changed slightly since the last time we took a run at that.) If she got a funded PhD program in Ireland or somewhere else in the EU... if Brexit went badly, it'd be an option. If Brexit was favorable, she'd need to look very carefully at her options on graduation. Living in Scotland again, and becoming a citizen, would probably be not in the cards for her if she took that offer. I'd do a lot of sighing, but it'd be her choice.
The Irish legal eagle I consulted last year informed me that Irish is Irish is Irish, as far as "settled in the UK" goes. [Unless they change it, which is always a lurking threat.] Realistically, when it comes down to it, I'd probably go with the Daughter anyway. She's all the family I've got. What am I going to do here on my own, spend my days counting the leaves falling and the number of squirrels mooching my peanuts over in the Botanic on my daily walks? I really, really, ~really~ like it in Glasgow, but ?
So, if we're tossed out, we go to the EU. Unless the EU won't take us. In which case we have no place else to go but back to the USA until other opportunities arise. All of that is completely out of our hands, at present. We will simply have to bob up like a cork, and float on whatever flood descends on us. I thank the gods we have options that do not include being returned to a third-world country where our lives might be in danger. (Or, more danger than on a typical trigger-happy day in the USA.)
From a position paper I read recently I understand that there are an estimated 500,000 legally-present, non-EU people in situations similar to the Daughter's, as of the time of the writing of the article. (Not including students.) They will not have 5 years' residence as of March 2019. Even with the tossed-around extra two years' transition period, many will not have 5 years at the end of that time. And, at that point, they'll have to pay again whatever charge the UK chooses to levy to be considered for further time in-country to make that magic 5-year mark. Assuming they are allowed to stay at all. All we, and anyone else, really, have are "assumptions" about what "might" happen at this point, and it's rather challenging planning for the future when you have no freaking clue what "the rules" will be. (No wonder businesses are getting seriously nervous!)
Although we applied for and received the Daughter's permission to enter well prior to the Article 50 trigger, we did not physically set foot in the UK until a month later. So the "cutoff date" is critical for us and it's not being publicly discussed. We are, in effect, like so many others in similar circumstances, hanging out in a very stiff breeze. If what TM said publicly is true and anyone "who is here now legally" can stay after Brexit, there's no problem. [Until the next speech, when her (or her successor's) tune changes.
] In any event, flapping here is better than going back to Trump's America, which is more and more unrecognizable.
And if they drive the UK over the cliff with a no-deal Brexit? The Daughter says she has met quite a number of people who only voted "no" on IndyRef because they were afraid an independent Scotland would not be allowed to remain in the EU. Apparently there've been several statements recently by EU officials stating the Scotland would be more than welcome in the EU, if it went Indy. So, one has to wonder what Scotland will do if it's a hard Brexit and the powers that should be devolved to them are not. (Apparently there's history there.
) IndyRef was only defeated by a very slim majority the last time. I am given to understand that there are a lot of people who voted "no" who are now seriously ticked off by what has/has not happened since that time.
But on the larger scale, this is all like watching a train wreck in slow motion. We will always bob along on the top of it, one way or the other. But for so many people who are about to, if you'll excuse mah French, probably get screwed, it's just a sad, sad thing. Especially for those who have no clue what's coming and who cannot get off the the tracks.