This is all very well for situations arising in a local situation (by this I mean born in ROI for example & dealing with legal situations here in ROI). It gets more complicated when one attempts to proceed with a more international situation e.g. immigration to USA, Canada, Australia.
By complicated I mean not having to find & employ the services of a legal specialist, who more often than not charges unnecessary & costly fees (in my case US$2,225.00 back in 1988).
The only reason I posted what I did was because I have been in exact the situation as the OP's daughter, never having foreseen the problems until it was too late, & on my doorstep.
I'm not claiming there is as others have said 'a problem doing this', or that she cannot 'do this'. I'm stating that the OP's daughter should think carefully about whether or not she really wants to go ahead 'with this', as it could lead to problems in the future.