My family has never had much money, so I'm quite concerned about my sister's shopping habits. I assumed it was quite average behavior for a young girl to plead for money for the school book fair, the ice cream shop, makeup, etc., but she recently was given a dog-walking job by our neighbor and has starting spending every cent she makes.
Almost as soon as she's paid she'll bike over to the mall and start buying little trinkets and things. Sometimes she'll lie about how much money she has and beg our mother for some amount of money to buy something she desperately needs. She does the same once she's spent all her money and there are often long circular arguments that end with our mom getting too stressed out to continue and just caving in.
I've tried talking to her as her older brother and explaining why she needs to save money, how she'll want things later that she'll need to save her money for now, and how it's unwise to be wasteful of any resource, especially one that for us is scarce. This didn't work.
I tried explaining to my mother that arguing for hours about the same thing and then just giving her money is counterproductive and that she needs to make a decision and then consistently follow through with it. This didn't work either.
How normal is it for a preteen girl to spend money like this and to beg for that money when she doesn't have it? What can I do to stop it?