If she was born in 1782 she would have been underage at her marriage 19 Oct 1802 (not recorded as such). There was also an Isabel Creer bapt. Maughold 11 Apr 1779, daur of John Creer and Ann KINREAD.

I couldn't see any Isabel Kerruish in the 1841 Maughold census.

The only one I noticed of possible interest to you was:
16 70 Rone
John KERRUISH 82 Farmer Isle of Man
Cathrine KERRUISH 20 Isle of Man
Isabella CUBBON 8 Isle of Man

Are you not a member of the FHS? Tom Corteen's transcripts of the 1841 and 1861 Maughold censuses are in the FHS members-only section of www.isle-of-man.com.

Sue