Nora is a British co-worker of Robin who was invited out with some of her friends as a way of protesting Valentine's day. Unbeknownst to them, Nora loves Valentine's day and romance and hopes to one day get married and start a family. Barney initially tries to exploit this, only for Nora to see right through his play. From that point, Barney began to develop feelings for her.
She has a playful side to her, agreeing to play laser-tag with Barney after being set up by Robin. Barney flat-out lies to Nora by saying that he wants to settle down someday. His conscience catches up with him before he can sleep with her by confessing, only to get slapped. Nora refuses to speak to Barney afterwards, but its clear Barney has fallen in love with her.
Barney later sees Nora, who has had time to cool off. The two have a brief chat, in which Nora hints at starting over. Barney then tries redeeming himself, eventually winning Nora back. When Barney's half-brother meets Nora, he reveals that she's alarmingly similar to their mother and that Barney must be suffering an Oedipus complex. That night, Barney and Nora go on a date which might lead to sex, but several things go wrong such as Nora breaking a tooth and a depressed man ruining the mood by committing suicide right outside Barney's apartment. Barney almost freaks out when he notices how similar Nora is to his mother, but is able to look past this as his mother is the coolest person he knows.
After Barney and Robin cheat on their partners with each other, Barney decides to come clean to Nora and they break up.
Some time afterwards, Marshall meets up with Nora who, still feeling upset about Barney's unfaithfulness, kicks him in the groin and slaps him across the face. This was all part of Marshall's plan to harness the fury of Barney's ex-girlfriends into a single concentrated slap.
Barney's last steady relationship was with his friend Robin, who just so happened to be Nora's co-worker. Barney and Robin showed lingering signs of getting back together, but Nora appeared at a crucial moment and distracted Barney. Robin then became increasingly jealous of Nora, but still supported their relationship. While sharing a cab ride together, Barney and Robin both had a lapse of conscience and spent the night together. The next day, Barney and Robin admitted they were still in love and agreed to split up with their partners. Nora then leaves Barney.