In the history of successful Spencer marriages, Georgiana could not include herself, however her brother, parents, and Spencer grandparents all could boast of happy unions.
Georgiana's paternal grandmother was born Georgina Carteret, daughter of the Earl Granville which was such a strong Whig family that it frightened the Lord Lieutenant, Robert Walpole enough to practically banish the Carterets to Ireland. But what frightened Walpole was something of interest to the formidable Sarah Duchess of Marlborough. When it came time for her grandson and heir, the Honourable John Spencer (fondly known as Johnny) to form a convenient union, Georgina Carteret was at the top of Sarah's list. I mean that quite literally too! Sarah actually made up a list of suitable brides for Johnny and arranged them alphabetically. Not caring too much about the woman, and more the potential money from Grandma Sarah, Johnny picked the first person on the list which happened to be Georgina. Similarly Lord and Lady Granville also looked favorably on the match also due to the political connection.
Due to the matter-of-fact manner of the engagement, you might expect a miserable marriage followed by a tart-ish lifestyle to follow. Georgina was known for being smart, charming, and later in life, extremely patient. Despite having no emotional connection to Georgina, and not planning on retiring from his bachelor lifestyle Johnny scheduled their wedding for Valentines Day. Georgina walked down the aisle in white, wearing the Duchess of Marlborough's jewels which she managed not to lose despite spending the rest of her wedding day with her husband at the gaming tables as they partied into the night. Despite the relationship seeming quite doomed, Georgina was head over heels for her husband and turned a blind eye to his drinking and wenching and gambling and late nights and tobacco-chewing and kept mistresses.
Everyone watched Johnny's bad habits contribute to a premature death. His son, John (Georgiana's father) succeeded his father at age 11 when Johnny's bad habits finally caught up with him. A few years thereafter Georgina married William, Earl Cowper, making her a Countess.
Despite suffering from cancer which would later kill her, Georgina lived a long life unlike her husband, and John who would die shortly after her. She lived long enough to attend her granddaughter's marriage and become concerned over her becoming "much quieter than she was" soon after her marriage. Georgina died soon after in 1780 at the age of 64.