She became engaged to Galbraith Lowry Cole, the second son of the Earl of Enniskillen, but Sparrow, who was in contact with Wellesley, revealed that he still considered himself attached to her.

Pakenham feared that Wellesley felt bound by promises he had made ten years earlier and was in two minds as to whether to accept the proposal.

The couple were married on 10 April 1806,[4] St. George's Church, Dublin (while it was using a temporary chapel in Drumcondra), by Wellesley's clergyman brother, Gerald.

[4] With little in common, Wellesley could not help but give the impression that he found her poor company and although they had two sons, Arthur, in 1807, and Charles, in 1808, they lived apart for most of the time and occupied separate rooms in the house when they were together.

Lady Elizabeth Yorke commented that "her appearance, unfortunately, does not correspond with one's notion of an ambassadress or the wife of a hero, but she succeeds uncommonly well in her part".

Maria Edgeworth, however, found her "delightful" and "amiable" and commented that: After comparison with crowds of other beaux spirits, fine ladies and fashionable scramblers for notoriety, her graceful simplicity rises in our opinion, and we feel it with more conviction of its superiority.Germaine de Staël described Pakenham as "adorable".

She ran a finger up his sleeve to find if he was still wearing an armlet she had once given him, "She found it, as she would have at any time these past twenty years, had she cared to look for it" remarked Wellington.