score:6
Telling the truth that your are married is correct and after giving the invitation letter and salary certificates. I don't think there wont be any issue at all. If possible, if you have marriage certificate, there are no chances to question your wife anything thereafter.
Upvote:3
So the advice here worked out fine for us. My wife is back in the country now. However for future reference - as a visitor a US citizen cannot spend more than 6 months within a 12 month period in the UK unless they have a valid Visa. I am now starting the process to get my wife a residence permit in the UK.