I had taken pride in not owning a mobile phone. I reasoned that I was not a doctor or a mountaineer, so I didn't need one. Watching people sally around the supermarket talking into their mobiles just made me think that their lives were not their own anymore. And imagine being out in a restaurant and having your meal interrupted by your spouse or offspring! No, I had no desire to feel indispensable. I put this logic to my daughter Eavan when she announced that she wanted one for her 15th birthday. "You're always the same - happy to live in the Dark Ages," she moaned. "Our family was the last in my class to go online and now I am the only one that hasn't got a mobile."

"What about all that radiation the phones emit?" "Oh for God's sake you used the same argument to put off getting a microwave and now we live on microwave meals."

It took a week to wear me down. On the day before the birthday I was frog-marched into a new phenomenon - The Phone Store - to see what was on offer. Gravitating towards the cheapest, it was immediately dismissed as "hideous". I hadn't realised that the mobile is a fashion item. "Its just not sexy," she told me earnestly.

It must be awful to have such a spoilsport for a mother. Last year she had waged a battle for a pair of runners costing £80. I won that one, arguing that the people who had made them in Vietnam were paid a pittance and that the huge profits went on marketing. But this time the same argument was falling on deaf ears. "Look" she enthused, "a mobile, an organiser and a watch for £99. That is brilliant value."

Of course. Why be so mealy-mouthed and just buy the mobile? Why not spend more money and get a watch and an organiser - despite the fact that she had a watch and a diary. But there I go again . . .

The purchase was made. A pay-as-you-go model with no monthly charges, but 80p a minute for each daytime call. For someone who spends hours on end on the landline phone, this seemed a little cruel, but then the financing of it has been agreed: she has promised to do it herself from her babysitting money.

In 20 minutes she knew how to credit her card, record a greeting and work the text messaging. I was impressed and began to think she was right to plummet herself into the new world. But a day later I had changed my mind. The text messaging never stopped. Birthday wishes came at the rate of every five minutes, with a ringing tone to indicate their arrival. And of course they had to be acknowledged. She seemed to call everyone she knew. Then came the accessories. Eavan's biggest thrill was discovering a mobile phone purse holder with a designer's name on it. It had to be had. As we were making this purchase a phone rang in the shop. There was a flurry as about 10 teenagers fumbled in their bags. It was Eavan's. "Where are you? Ooh. Really. I'll ring you later." It rang again.

"Hi. Can't talk. What are you doing? Ring me later - on the mobile."

And within 48 hours all the credit was used. The urge to chatter is expensive. Expense is the operative word in rearing a teenage girl. Eavan flabbergasts me with her knowledge of designer labels, perfumes and even the latest "in" food. Everything must be had and sometimes it can be difficult for her to take on board the economics of family life. But that's what growing up is all about, I suppose.

Deirdre Morrissey is a copytaker with The Irish Times. She is the mother of three children and has been contributing to the Parent's Diary column for the last four years.