She doesn't have a job description, there are no performance parameters for an MP. It is up to the individual how they best represent their constituents
Sinn Fein currently have 7 elected MPs who have never sat and have no intention of sitting in the HoC, I'm not sure you could even introduce rules such as people are suggesting in relation to Dorries without causing mayhem in NI. You can't have one rule for one, one rule for another. Now admittedly, the SF MPs are always elected on the understanding that they will never sit but all the same, you still be having new by-elections in NI every few months in those 7 constituencies