If you want a fucked-up mythological conspiracy theory, there's a non-zero amount of evidence suggesting that Emer had planned around/for Forgall (her father)'s death, because the process of Cu Chulainn going to retrieve Emer from Forgall's castle lines up worryingly well with the marriage conditions Emer laid out for Cu Chulainn, with startlingly little consequence for Emer herself outside of Forgall dying.
The fact that she (roughly, varies in exact wording from translation to translation) phrases a part of her marriage conditions as, "and struck down three groups on nine men, leaving the middle one alive", and then when the time comes for Cu Chulainn to start fulfilling the condition, Emer's brothers Scibar, Ibor, and Cat just so happen to be the middle man of each of the three groups makes this suspect as hell.
Now, am I saying this is at all what Ancient Irish bards telling these stories intended? Probably not. Is it fun and kinda funny to think about? Very.
*Translation of Emer's line comes Thomas Kinsella's "The Tain"
