I can see one Margaret Cannell in Ramsey, birthplace Michael at the 1851 census. She is with John Cowin (Ballaugh) and wife Elenor Cowin (Michael), address Moores Brewery. She is listed as 'cousin' aged 23 and is a 'house servant'. Not much help I know.

I think it is possible for the father to be a (farm?) labourer at the baptism but a farmer by the time of her marriage, 20 years later or so. In my tree I have several instances of a farmer's son being a shoemaker or somesuch for many years before taking over, or helping to run, the farm.
What seems less likely is that he would be a tailor - the only James Cannell of a suitable age that I could spot in Kirk Michael - in the same year as farmer. Of course, there's always the possibility that Margaret's father had died before the census. By the way, I'm not following this family - I just thought I'd have a quick look at the census for Margaret.