There’s a speculation that has Finovula as a daughter of Alexander
https://ancestorium.com/tng/getperson.php?personID=I025688&tree=1
Her parents here are a guess based on dates. In Burke's Peerage under "SUTHERLAND, Countess of" it says she was daughter or granddaughterr of Archibald/Celestine Macdonald
Which I find bizarre, as that narrative should put her one to two generations below. That’s probably what you kicked her off of before, quite correctly.
It turns out there was a mid 1300’s Finovula Macdonald married to a John Stewart, so that was another time traveling mixup.
There’s a chart with Celestine’s daughters, and I think I saw a legit reference to Finovula sometimes known as Margaret. Yes, here it is.
Fynvola (Margaret) Macdonald of Lochalsh b 1476 m Ewen Allenson
https://ancestorium.com/tng/getperson.php?personID=I013318&tree=1
This girl would be too young to be the Sutherland wife, I think.
(I’ll look for better refs)