Hi Greg,
I agree with Frances, she could have been left behind.
Another thought--perhaps she was omitted accidentally from the passenger list. There are other instances where that has happened.
Both the 1830 and 1840 U. S. census, which do not give any names other than the head of family, have female children indicated which could be Catherine.
In 1830: a female under 5--could be Catherine, which would mean that Eleanor was not included (perhaps born after the census?)
In 1840: a female 10-15 could be Catherine.
In both cases, the age is slightly off, but that is not uncommon.
I wonder if she is listed in the 1841 IOM census.
Lois