On 5 July 1794 she married Henry Conyngham, Viscount Conyngham, and they became the parents of five children. In 1797 he was elevated and became Earl Conyngham. 
Frances, Lady Jersey, as mistress of the Prince-Regent, the future King George IV, had been replaced by Isabella, Lady Hertford, and the latter was replaced by Elizabeth, Countess Conyngham. Elizabeth remained George IV's mistress for the rest of his life. In 1816 Elizabeth's husband was elevated again, and became Marquess Conyngham. It was said that she received jewels worth œ80,000 from the king. In 1821 Greville stated: "She comports herself entirely as Mistress of the Household, lives in one of the houses in Marlborough Row and has presents of enormous value." And in 1829, he continued: "The wealth Lady Conyngham must have accumulated by savings and presents must be enormous; the king continues to heap all kinds of presents upon her, and she lives at his expense. They (Elizabeth and her husband) do not 
possess a servant; all such have situations in the king's household from which they receive their pay, while they continue in the service of the Conynghams. They dine every day, while in London, at St.James's, and when they give a dinner, it is cooked at St.James's, and brought up to Hamilton Place". 
In 1820 Elizabeth was a plump, handsome woman; the king was in love with her in his rather limited fashion, and some called it a misuse of language to call her the king's mistress as, probably, they never went beyond a little elderly dalliance. Society women thought her rather vulgar and not very intelligent, unlike the king, who considered her "wittier than any male or female of his acqaintance". 
She was careful to preserve appearances and never stayed under the same roof as the king without being accompanied by her husband. It was later said that, during George IV's last illness, she 
carted away sufficient jewellery, plate, etc., to fill two wagons. All the time she professed the greatest distress, and prayed with unction for his recovery. As was said: "First she packed and then she prayed. And then she packed again". She survived the king by thirty-one years. 
 

Source: Leo van de Pas