
Here is Simon's page: https://en.wikipedia.org/wiki/Simon_II_de_Senlis,_Earl_of_Huntingdo....
His Geni page incorrectly lists his daughter as "Amice" instead of Alice which could be the source of the confusion.
It appears that Amice de Senlis is correct: https://fmg.ac/Projects/MedLands/ENGLISH%20NOBILITY%20MEDIEVAL.htm#...
But Alice de Quincy must still be incorrect due to not being able to remarry.
All we have are Richard marrying an "Alice" in Yorkshire deeds and Yorkshire Archaelogy Journal vol 29 confirms the date of 1204-1209 for Richard de Thornhill's death and Alice's existence:
|https://archive.org/stream/YASRS065/YASRS065_djvu.txt
https://archive.org/stream/YAJ0291929/YAJ0291929_djvu.txt