"Your wife is marvelous."
Translation:Tha do bhean mìorbhaileach.
In principal it is not wrong, apart from the fact that it should be 'a' bhean agad'. Here is an example of the construction used in An Litir Bheag (Number 520):
An-uiridh, bha mi fhìn ’s a’ bhean agam a’ cur seachad beagan làithean air a’ Chomraich.
(Translation: Last year I and my wife were spending a few days in Applecross.)