As part of a plan to get information on Howard Stark, Cassandra's mother had her draw the attention of Howard's (secretly foster) son Tony when he was studying at the University of Cambridge. After weeks of having Cassandra on his sights, Tony approached her during a party. In the middle of a scuffle, Tony and Cassandra slipped past her bodyguards. They eventually caught up to them and took her back.
The following days, Tony and Cassandra got to know each other better, causing her to develop real feelings for him. She eventually invited Tony to have dinner with her family. At the end of the evening, Tony and the Gillespies were attacked by Hydra forces, who had targeted Cassandra's mother because she had "betrayed" their cause. Stark managed to take a gun from one of the Gillespies' fallen bodyguards and kill a Hydra soldier who had Cassandra's mother at gun point; however, Cassandra's father, Giorgio, was allegedly severely wounded during the shootout.
After learning of Tony's involvement with the Gillespie, Howard forced his son to return to America, but Tony still managed to slip away and travel to England off the grid in order to reunite with Cassandra. The two lovers ran away to navigate the oceans in a sailboat. During their cruise, Cassandra confessed to Tony that while she held feelings for him, their relationship had started as a ploy of her mother. Tony docked in the port of Auckland, New Zealand and stormed off the boat to get away from Cassandra, who tried to convince her that her feelings were real, to no avail. Forces of S.H.I.E.L.D. led by Howard Stark soon appeared on the bay to recover Tony and arrest Cassandra. They were interrupted by an assault from Hydra forces, which abducted Cassandra during a shoot-out with S.H.I.E.L.D. That was the last Tony saw of Cassandra for decades.
Twenty years later, Tony Stark, as the super hero Iron Man, crossed paths with Cassandra when he was trying to find out about his true parentage, following the discovery that Howard wasn't his real father. Cassandra's Mandroids managed to catch Iron Man by surprise and knock him down. When Cassandra left the scene and had the Mandroids deal with Tony, Stark surrendered and let them take his suit. Gillespie's men brought Stark's armor to their boss at her compound, unaware that his advanced technology allowed him to use an undetectable tracker to find Cassandra's whereabouts. Equipped with a spare suit, Tony confronted Cassandra, and tried to force her to reveal any information she could possibly know about his father, considering his investigation led him to her. Cassandra revealed that she didn't know anything, a fact the sensors of Stark's armor confirmed as true.
Gillespie's Mandroids arrived to the scene and surrounded the compound. Stark stalled for time until his A.I. assistant Friday could hack into their systems and cause the Mandroids to fire at and strike down each other. Cassandra attempted to escape, but she was intercepte in her car by Friday, who was controlling the armor the Mandroids had previously confiscated. Gillespie was subsequently arrested by S.H.I.E.L.D. agents.