Hi Ecneps,
Could she actually be the daughter of John and Eliza Cavanaugh, whose age is unclear on the 1871? It could be a mistake by the enumerator in 1881, putting her down as daughter instead of granddaughter to Eliza Dean, and then logically putting her surname as Dean.
In case you don't have it:
RG10/4792/140/13
5 Henry St, Myton, Holy Trinity, Yorkshire
Ann E Cavanaugh, Head, Mar, 27, Fisherman's Wife, Hull
Charlotte Cavanaugh, Daur, 8, Scholar, Hull
Ann E Cavanaugh, Daur, ?, Scholar, Hull
James Cavanaugh, Son, 1, Hull
MJP