Isabel de Saint Amand - date of birth seems wrong

GENI states her husband Amauri de St. Amand, II was born abt 1235.
Amauri de St. Amand, II

This profile for his wife states she was born circa 1213.
Though not impossible, it seems unlikely Isabel was born 1213 and was 22 years older than her husband.

I've not found a primary source for her date of birth, and would only guess she was born say 1230 or later, based on the date of birth of her husband and her children.