Precisely why I'm confused. I have the record for this on ancestry ad also her marriage to Thomas Hall, though cannot find another Elizabeth Haddock which 'fits'.
The only possible theories I have are:
Elizabeth was a bigamist (doubtful shed do this in the same place)
Elizabeth and Pendleton divorced, she lost her legal protection which came with marriage, and with it her married name.
To add to the confusion, Thomas Hall and Elizabeth Haddock married in March 1829, their eldest son was baptised in November 1830. However on the 1841 census, he has a sister, a year older (i.e. born at least 1829). It seems Peter was born a while before his christening, and so assuming a normal term pregnancy, Elizabeth was most likely pregnant before the marriage. I've no record of Mary's baptism so cannot be sure of date of birth, however, which fits.