Episode 21 of "Grounded for Life"
s02e06 Smoke on the Daughter

During a stressful day at work, Claudia takes a puff of a co-worker's cigarette which quickly turns into an entire cigarette and then a daily habit. Desperate to keep her smoking habit from Sean and the kids, Claudia tries her best to smoke without being found out, but is busted by Lily. Lily makes a deal with her - she won't say anything if Claudia will get her a cell phone and Claudia agrees. Sean thinks that Claudia's bizarre behavior lately has something to do with him, prompting him to buy her the expensive armoire Claudia was admiring recently at the flea market. When her quest for a cigarette leads to her digging through the trash and landing outside Brad O'Keefe's window, she realizes she has hit a new low and swears off her habit. Meanwhile, after setting a date with Dean on her new cell phone, Lily is humiliated to find out Dean heard her gushing about him when the phone didn't turn off.