The difficulty is with the person they have speaking on the app..She is from Connacht which has a very different dialect to the rest of Ireland and they pronounce things very differently there..They should have a Gaeilge speaker on here with a more universally recognised and dialect that is easier to understand
As a rule it should be pronounced cairéad..but unfortunately they are using a Connacht dialect here on the app..Connacht people have very different pronunciations which differ to most of the rest of Ireland..eg..the verb to work 'obair'...Most people prounce that as 'ub-ir'.....Connacht speakers prounce it as 'ib-ir' which throws me every time I hear it..They also tend to ignore sineadh fadas..and pronounce 'mh' and 'bh' as 'w' instead of the most commonly used 'v' sound....Connacht speakers also have a habit of omitting letters from a word when speaking..So it can be difficult to undestand them.. ..I find it confusing myself on here and I regard myself as a near fluent speaker of Gaeilge.
http://en.wiktionary.org/wiki/d%C3%A9an#Irish (the first Etymology which follows to http://en.wiktionary.org/wiki/Appendix:Proto-Indo-European/%C7%B5enh%E2%82%81- - the link is not valid without the hyphen at the end, you have to copy the whole link from here or just write it in address bar at the end of the address)
As you can see they have nothing to do with each other :)
Because the "i" in bia and siad is the nucleus of the stressed syllable. In general, all the vowels that are NOT in a stressed syllable are reduced to schwa. So, as the "i" in "taitníonn" is not the nucleus of the stressed syllable (it's "ai"), then it needs a fada not to be reduced to the schwa sound.
Of course there are cases where you have a fada over a stressed vowel. The reasons for that are a bit different though. It's related to pronunciation too, though. Sometimes it's there to make clear which vowel is the "sounding vowel" and which one(s) is(are) there just for the "caol le caol agus leathan le leathan" rule.
I keep hearing added sounds in these spoken sentences, a v here and there and an m sound instead of or with n. I have looked at some Irish grammar books lately, and some of them state at the beginning that they are using Connacht dialect, which must be becoming the standard.