Can someone please, please help with flight information?

[Hairywoes]

My mum needs to fly back from the Republic of Ireland to England.
Does she need to have any covid tests before/after flying? I’m reading conflicting advice online.

She’s fully vaccinated, if that makes any difference, but she’s over 70, doesn’t have a smartphone and has no clue how to use technology so arranging tests and getting results emailed is proving to be a nightmare.
I’m trying to sort her a flight back but I’m in England so limited with ways to help.

Can anyone help clear this up for me? Does she need a LFT before flying? Day 2 PCR? Locator form?

If anyone could help I’d be forever grateful!

From Ireland to UK there are no tests, no vaccines, nothing.
This is ever evolving though, so I imagine it would be no harm if she had her vaccine status available (if she is vaccinated).
Tests are needed from UK to Ireland but not for return (provided she has not left the common travel area in the last ten days.

www.citizensinformation.ie/en/government_in_ireland/ireland_and_the_uk/common_travel_area_between_ireland_and_the_uk.html

Thank you @UpsilonPi really appreciate your help!