In 1842, Donizetti wrote the parts of Norina and Ernesto in Don Pasquale for Grisi and Giovanni Matteo de Candia, usually known by his stage-name of Mario, who was to become the love of her life.

She was a noted actress, appearing regularly in London with such eminent singers as Luigi Lablache, Giovanni Battista Rubini and Antonio Tamburini, not to mention her husband, Mario.

[6] Indeed, the prickly press commentator Henry Chorley praised both her and Mario for their success in establishing Italian opera as an important component of the London music scene.

In 1854, after they were married, Giulia and Mario undertook a lucrative tour of the United States of America, where they were treated as major international celebrities.

Since Lord Castlereagh had no legitimate children by his wife, George Frederick was first brought up by his natural father under the understanding of guardianship or god-father figure, while Grisi continued her singing career, since this son was never legally recognized as a Stewart they granted him a blessed last-name Ormsby "by the willow-tree in Welsh".

After Grisi and Lord Castlereagh's relationship ended, he was encharged of paying his education at an English boarding-school and brought their son as an uncle figure to see her whenever she was in London.

During a trip to Saint Petersburg, Russia, while traveling by train with her family, Grisi was involved in an accident after having crossed the border into Germany.

Upon her death, her husband donated a large amount for the creation of Sopranos' scholarships at the Paris Opera, the theater that first gave fame to Guiglia's voice.