She was friend of George Frideric Handel, most likely meeting him at a social gathering hosted by her close companion, Mary Delany.

Donnellan and Delany were in the small audience hearing the first rehearsals of Handel's Alcina (1735) and Imeneo (1740) operas.

Donnellan's four Hanover Square properties were all located very close to Handel's residence, as seen in a 1747 map of Southwark and London.

After meeting Samuel Richardson in 1750, they became frequent correspondents and close friends, with both of them leaving a bequest of mourning rings in their respective wills.

Donnellan's siblings died in quick succession in 1751 and 1752, which resulted in trauma due to disputes over their wills.

[1] She left a bequest of a quarter of her assets, £1,243, to Trinity College Dublin, which was to be used to promote "religious learning and good manners."