Not much is known about Gertrude Jacks' past, although she acknowledges that she worked for S.H.I.E.L.D. under both Nick Fury and Tony Stark's direction (and presumably Maria Hill's too). Sometime in the past she met the mutant known as Maverick and the two dated, although it never worked out, they remained friends.
When Norman Osborn assumed command of the global security network of America and re-christened S.H.I.E.L.D. as H.A.M.M.E.R., Jacks remained an agent and justified working for a maniac like Osborn by pointing out that both Fury and Stark were also maniacs in their own ways.
Gertrude Jacks was created by Jason Aaron and Ron Garney and first appeared in Weapon X #4.
Gertrude Jacks didn't appear again after her initial appearances in the first story arc of Weapon X and her ultimate fate was left unrevealed for years. In Wolverine #304, Jacks is mentioned by Maverick and Wolverine and we learn what came of her following her first, and only, appearances.
Major Story Arcs
When someone had stolen the Weapon X files and sold them to a company called Blackguard, Maverick and Wolverine set out to stop Blackguard's Weapon X-inspired soldiers, Strikeforce X, from becoming sanctioned by the Government. Jacks was among a team of H.A.M.M.E.R. agents investigating murders related to Blackguard and she would exchange info with Maverick about the case.
Later, when Wolverine fought one of Strikeforce X and collapsed in exhaustion afterwards, Jacks and two other H.A.M.M.E.R. agents arrested Wolverine. After transporting Wolverine back to a holding facility, Jacks secretly let him go.
She and Maverick later broke into Blackguard's offices and deleted all the Weapon X files to ensure nobody else, Norman Osborn included, could learn how to create more Weapon X experiments. Maverick proposed the two of them run away together, him clearing still having feelings for her, but Jack declined and reminded him that they didn't work well together.
Unfortunately for Jacks, her decision to remain working as a H.A.M.M.E.R. agent comes to a nasty end when her duplicity and "treasonous" actions were quickly discovered by Norman Osborn. Osborn had Jacks captured and imprisoned in a gulag in the middle of nowhere with no hope of release or rescue.
Back in Japan
Quite some time later, Maverick became depressed and suicidal but while in contact with Wolverine tried to convince his friend he wasn't about to kill himself. Maverick claimed that he was happy and planning to marry Jacks whom he had supposedly broken out of Norman Osborn's prison. Wolverine immediately proved this to be a lie when he pointed out that he had personally had Jacks released from prison some months ago and that she was now living in Tangier with another man.
Powers and Abilities
Gertrude Jacks has no superhuman powers but has S.H.I.E.L.D. training and as such is skilled in armed and unarmed combat.