Marriage to Dónal an Chogaidh (Donal "of the war") Ó Flaithbheartaigh brought her greater wealth and influence, reportedly owning as much as 1,000 head of cattle and horses.

In 1593, when her sons Tibbot Bourke and Murchadh Ó Flaithbheartaigh (Murrough O'Flaherty) and her half-brother Dónal an Phíopa ("Donal of the Pipes") were taken captive by the English governor of Connacht, Sir Richard Bingham, O'Malley sailed to England to petition for their release.

O'Malley is not mentioned in the Irish annals, so documentary evidence for her life comes mostly from English sources, especially the eighteen "Articles of Interrogatory", questions put to her in writing on behalf of Elizabeth I.

[7] Although under Brehon Law only male members of the derbhfine could inherit the mantle of Chief of the Name through tanistry, O'Malley "was considered to be the legal retainer of the family land and seafaring activities".

[8] With shore castles like Carrickkildavnet, the Clan Uí Mháille demanded and received black rent from those who fished off their coasts, which included fishermen from as far away as England.

This earned her the nickname "Gráinne Mhaol" (Irish pronunciation: [ˈɡɾˠaːn̠ʲə ˈwiːlˠ]; from maol, meaning 'bald' or 'having cropped hair'), usually anglicised as Granuaile (/ˌɡrɔːnjuˈeɪl/ GRAWN-yoo-AYL).

As Ó Flaithbheartaigh tánaiste, Dónal an Chogaidh had expectations of one day ruling as Lord of Iar Connacht, which was roughly equivalent to modern Connemara.

O'Malley then returned to her own lands and established her principal residence upon Clare Island (now called Granuaile's Castle).

Seeking vengeance, O'Malley attacked Clan MacMahon's stronghold of Doona Castle in Blacksod Bay and slew her lover's murderers upon Caher Island.

The thief dug a tunnel and escaped, however, and the hermit who took care of the church broke his vow of silence to scold her for attempting to harm someone who had sought sanctuary.

[18] More than twenty years after her death, an English Lord Deputy of Ireland recalled her ability as a leader of fighting men, noting the fame she still had among the Irish people.

[23] Grace's half-brother Dónal na Píopa was also arrested by Sir Richard Bingham and charged with the murder of some English soldiers.

[23] Tradition but not the written sources states that O'Malley met with the Queen at Greenwich Palace, wearing a fine gown; the two of them were surrounded by guards and the members of Elizabeth's royal court.

[23] The Queen ordered her Privy Council to seek an explanation from Sir Richard Bingham regarding his treatment of O'Malley and her family and to investigate how her situation could best be relieved.

Bingham defended himself replying "in defence of my own innocency ... to shew me instance of any one that ever I used violence against, havinge always (I thancke the Lord) had that consideracion of christian duty as I never sought any man's bloode otherwise then by course of her Maties.

"[23] He made his thoughts clear that "how great soevr any may make her wch knoweth her not I will nevr aske but a boat of xxx tonnes to beate her ... and wth gods assistance dryve her and all her fleet into the sea.

[23][25] Sir Richard Bingham disagreed with the decision of the Queen and initially did not obey her instructions, which O'Malley had personally delivered to him on her return to Ireland.

Therefore, he reluctantly agreed, "to enlarge Grany O'Mally, her son Tibbott and her brother Donal na Pippe, ... upon such slender surytes.

Bingham struck, quartering a troop of his soldiers on her ships to accompany her in her voyages and later forcing her into service against some of her own kinsmen who he claimed were in rebellion.

Unable to bear the strain, she, her sons cousins and followers "were forced to withdrawe themselves into the Province of Mounster, where they do remaine in great distresse".

O'Malley was rewarded when in August 1595, a commission was granted by the queen and the Privy Council to investigate the lands in Mayo claimed by her two sons, her grandson Dónal O'Flaherty, son of Owen, Dermot and Dónal O'Malley of "Owel O'Maillie", and Miles MacEvilly, Tibbott-ne-Long's foster-father, "with the intention of the Queen accepting their surrenders of the premises and re-granting them by letters patent.

In her 2006 biography of O'Malley, Irish historian and novelist Anne Chambers described her as: a fearless leader, by land and by sea, a political pragmatist and politician, a ruthless plunderer, a mercenary, a rebel, a shrewd and able negotiator, the protective matriarch of her family and tribe, a genuine inheritor of the Mother Goddess and Warrior Queen attributes of her remote ancestors.

The Ó Máille family "book", a collection of eulogistic bardic poetry and other material of the sort kept by aristocratic Gaelic households of the period, has not survived.

[2] She is also mentioned in the English State Papers and in other documents of the kind, an example being a letter sent by the Lord Deputy, Sir Henry Sidney, to his son Phillip in 1577: "There came to mee a most famous femynyne sea captain called Grace Imallye, and offred her service unto me, wheresoever I woulde command her, with three gallyes and two hundred fightinge men ..."[3] Local traditions concerning her were collected by Irish scholar John O'Donovan in the 1830s and 1840s on behalf of the Ordnance Survey of Ireland.

[30] Westport House in County Mayo, Ireland, was the seat of the Browne dynasty, Marquesses of Sligo, direct descendants of Grace O'Malley.