She was the eleventh and youngest child of Sir Nicholas Bagenal, a prominent Staffordshire soldier and Marshal of the Irish Army, and his wife Eleanor Griffith of Penrhyn, Wales.
[6][1] Before Nicholas's death in February 1591,[5] he charged Henry with the "careful disposing" of Mabel[2] and he forbid her from marrying a Gaelic Irishman.
[7] Tyrone had ambitions to rule over Ulster, and was greatly offended when, in 1590, the lands of his late urrí[a] Hugh Roe MacMahon were divided and granted to Henry rather than himself.
[9][14][15] Henry was alarmed, and kept Mabel out of Tyrone's reach by sending her to live with their sister Mary (wife of Patrick Barnewall) in Turvey, County Dublin.
[9][2] Henry referred the decision to the queen and privy council, claiming that his sister was not prepared to live in what he termed an uncivil Gaelic household.
[7][2] A number of prominent officials, including Archbishop Loftus and Sir Geoffrey Fenton, believed that an alliance between Tyrone and the Bagenal family would be in the public interest.
[2] Tyrone wrote to the Privy Council: "I dealt with [Henry] at least six several times for his consent; I offered to put in sureties for the assurance of a jointure to his sister; this I did before good witnesses".
[17] It is possible Tyrone's judgment was impaired by his feelings,[2][18] though most historians believe that he recognised the advantages of marrying into the powerful Bagenal family.
[22][27] After being assured of Mabel's free consent,[2][9] and for the sake of her reputation,[28][27] Jones married the couple on 3 August 1591[2][27] at Drumcondra Castle.
He was infuriated "that my blood which in my father and myself hath often been spilled in repressing this rebellious race, should now be mingled with so traitorous a stock and kindred".
[35] That same month, the couple reached a major crisis when they clashed over the assassination of Henry's client Phelim MacTurlough O'Neill, which Tyrone had orchestrated.
[2] Historian Jerrold Casway believes that despite the romantic circumstances of their courtship, the marriage "probably ran its course" and Tyrone would have continued with his concubines.
[6][32] According to Tyrone himself, "because I did affect two other gentlewomen, [Mabel] grew in dislike with me, forsook me, and went unto her brother to complain upon me to the council of Ireland, and did exhibit articles against me".
[2][17] At the time of Mabel's death, Tyrone was feigning reconciliation with English authorities[47] whilst secretly holding out for the 2nd Spanish Armada's arrival.
[31] The Great O'Neill (1942), an influential biography of Tyrone by Seán Ó Faoláin,[8] has been criticised for its overdramatisation,[53][54] particularly for overtly romanticising Mabel's marriage.
[55] The Great O'Neill was used by Brian Friel as the basis for his 1988 play Making History,[8][21] where Mabel's marriage to Tyrone is a central topic.
[58][59] Maria Gaviña Costero notes that Friel shifts Mabel from "a historically marginal position to the decisive figure she is in this play",[60] and portrays her with greater agency and depth than Ó Faoláin.