I don't understand why people are so quick to discount that a single unemployed mother would give Xanax to their daughter because it costs $10.
First, she wouldn't give her a whole pill. Probably, 1/4 pill would be enough... therefore, $2.50.
Second, yes, Tylenol PM or Benedryl are cheaper BUT some kids aren't knocked out by it. Some kids (including mine) get hyperactive instead. (No, I didn't drug my kids to knock them out. They have allergic reactions to different things. The doctor says give them Benedryl for it and the next thing I know is that I don't get sleep for the next 24 hours.) She might not know the dosage either (it's not on the box and most doctor's won't tell you unless they see symptoms in person -- at least mine won't). But imagine this scenario: another club kid comes up to her says, "Come party with me tonight at ___". Casey says, "I can't, I got my kid". Club kid says, "That's ok, I've got a Zanny. We'll break it in half (or a quarter) and she'll go to sleep and we can party. My (sister, friend, roommate... insert word of choice here) does it ALL the TIME!"
Third, Casey STOLE close to $30,000 from family and friends in about a very short period of time and doesn't appear to pay room or board. How much money does she need? And if she does other drugs, I'm sure the dealer throws in the Xanax on the side if she spends enough.