After Charlie cancelled his wedding to Mia, he met and began dating Lydia. Lydia had many characteristics of Charlie's mother, she was bossy, manipulative, had a job in real estate, and even dressed like her. Alan, Berta, Jake, Rose, and even Evelyn noticed it, for some reason Charlie did not. When Charlie saw Lydia treating her sons like Evelyn treated him, he was going to break up with her, however Lydia's sexual attractiveness won out, and Charlie continued seeing her. When Lydia began bossing Berta around she threatened to quit. Charlie told Berta he stopped seeing her, but was actually just keeping the relationship secret. Berta eventually caught them in bed and quit her job right on the spot. Charlie broke up with Lydia and got Berta to work for him again, but only if Charlie attended sex addict seminars.
In "Gumby with a Pokey", Lydia re-appeared as a hallucination Charlie had after smoking prescriptive marijuana.
In "Nice to Meet You, Walden Schmidt" she along with a lot of Charlie's old girlfriends appear at his funeral.