It's because of her age. If she were much younger, it might be arguable. But adult children have no place in their process, it seems. They are lumped in under "other family members" and not part of the nuclear family. And it's a tough row to hoe to get one of those approved, I'm told. (
Recently on another forum, Polish citizens were asking if they could use their elderly parents in the UK, to live in the UK themselves and bring their adult child with them. They were told they would need their own visas and their adult child would need his own visa too.
I assume your daughter has looked to see if she can get a UK work visa?
The remaining naturalization option we have applied for her under is "association" - close association with an Irish citizen. It's an option that the Minister of Justice can approve as he/she sees fit. It has not been denied yet - but it has not been approved, either.
Let us know how you get on. Somebody I know is from Irish descent, but he didn't have Irish citizenship. He had to work in Ireland to then naturalise as an Irish Citizen. He had been hoping to pass Irish citizenship on to his adult children but was unable to do so. If anybody can find a way, you can.
We've looked at a few other countries, yes. Each EU country has it's own little quirks. Germany seems like a logical place, but their issue with foreigners right now isn't ideal.
It's the same in every European country that was/is very popular with immigrants.
Since neither of us is really fluent in a foreign language, it's a little difficult. She's got some French, and we both have a very little Spanish. She also has a degree in Japanese, but that kind of is pointless here....
Malta? They speak English. Before Brexit, many non-EEA immigrants who naturalised as British and who wanted to bring elderly non-EEA citizens to the UK, used Malta for the EU Surinder Singh route. The earlier ones used Ireland but the Irish took a long time to give them a permit. The UK had shut down the adult dependent visa to make it virtually impossible to get, to stop the burden on the NHS.
Most EEA countries speak English as it's the business language of the EU. What about Portugal? They have a large number of British (and German) communities who retired to that country and they will speak English. It's a good source of revenue for Portugal as these retirees spend their pensions there and Portugal doesn't pay for their healthcare (until they have/if they want Settlement).
One of the loopholes to get her into Ireland would be to live in another EU country with her for a period of time, with her as a member of my household, and once officially accepted as settled in that country we could then move to Ireland. After a period of time there she could apply for citizenship via one of the other routes. At that time we could take advantage of the CTA. Unfortunately, all of that would take years.
And things can change in that time.
Perhaps also keep an look out for any new UK visas your daughter might be able to get?