If a soldier was married when he enlisted and chose not to take his wife with him into service than she was not a military dependant and not the army's responsibility.
If a soldier took his wife with him into service and she was not one of those chosen to accompany the regiment when it embarked for foreign service than the regulations allowed a small sum of money to be paid to her that would permit her to return to her home parish.
Choosing which wives were to accompany a regiment overseas was usually done by drawing lots, as it was the most fair method. This was a public event and the wives drew their lots to the accompaniement of much comment from spectators, depending on their popularity. There is a very moving description of this process in Joseph Donaldson, RECOLLECTIONS OF THE EVENTFUL LIFE OF A SOLDIER (1853).
Naturally, those women left behind were distraught as the chances were good that they would not see their husbands again. When the 1/23rd prepared to leave Colchester for North America in early 1808, the wailing of the wives who were to be left behind kept everyone awake on the night before the unit marched out.
DE Graves