Hi there, this isn't so much a step problem as such, maybe more a general teenager one but I've made the mistake of posting elsewhere before about my DSD and got a massive flaming for being such a wicked stepmother, so I thought I'd post here 
where it's safer (looks around sheepishly)
So, my DSD lives with her dad and I 3/4 days a week (7 days out of 14) so she needs a proper warddrobe here rather than carry clothes to and fro. Most of the things we buy her end up straying back to her mum's never to see our door again but that is besides the point and something we're working on (any tips on this would be great!)
Despite us having DSD 50/50, DP pays way over the odds for CM which I suspect is why we have a problem with clothing for DSD whereby he is loath to spend a lot of her as he is already paying out so much.
We have had several conversations where I have explained to him that the fact is, he chooses to pay over the odds. And that is not DSD's fault. As such he just has to swallow the fact that he has to kind of pay for her twice. i.e. once for things at her mum's and once for things at ours. He does get it, he's not a cruel person... but for whatever reason we always end up in a situation where DSD needs things, and he is reluctant to buy.
So that's the background. Anyway, what usually happens is that come a new season, (DSD is 13 and growing like a weed so needs new things all the time!) I notice she needs new clothes and ask her to come up with a list of things she needs (either by herself or we do it together) so that I can take her shopping. This is out of my own pocket and so not something I am obliged to do (DP and I keep our finances seperate). I explain that it is about getting her a new wardrobe of sensible things that she can mix and match and that will get her through the season.
What I want her to think is; "that's kind, SM doesn't have to do that for me but she cares about me and wants me to feel at home so has offered to take me shopping. I'll do as she says and think of a way to spend her money wisely, oh and I should probably say 'thank you' too"
What i actually get every time (and.I.never.learn) is something like what I got this morning on text
Me: Good morning gorgeous, it's getting really cold and you'll need a new wardrobe here. Can you have a little think and put together a list of things you need - you know the drill, not one off expensive thinks that don't go with anything, but some sensible stuff that will see you through the cold winter. If you can show me that you can be sensible then I'd love for us to go on a girlie shopping trip at the end of the month and i'll get it all for you xxx"
DSD: "can we get it all from Hollister?"
Me: "haha you're funny"
DSD "I don't see why we can't?"
Me:"because a jumper in Hollister is about £60 and you need a whole wardrobe, not just one jumper"
DSD: "Will you at least think about it?"
and so on and so on.... so I am left feeling like my offer has been thrown back in my face and isn't good enough for her. We will now get locked in to tense negotiations, I'll be bombarded by emails with links to Hollister this and that, her mum will be on the phone saying that if I pay for half of a Hollister jumper for her, she'll pay for the other half... DSD will eventually agree to give in and we'll go shoppoing for the "sensible" wardrobe but the trip will turn out to be a ruse to get me to go to Hollister where she'll beg and plead with me and eventually I'll tell her she's a spoilt brat and sulk off home.
On occassion it will result in me giving in and buying an item for her, feeling really good about it because i know how much she wanted it, and then watching her forget all about it 2 seconds later, start asking for something else, take the item to her mum's and leave it there and we're back to square one with nothing for her to wear when she's here.
This is what always happens. Why do i get involved???!!! And most importantly, now that i've started it all up again, how do I stop it in it's tracks before it gets out of hand?
I can't get over how spoilt she is. I would be mortified if my DD treated her step mum in this way. I know a certain amount of it is about being a teenager, but I have spoken to my mum and she said that I was always grateful when I was bought or offered something. I can remember going shopping with my mum and longing to go to the more expensive shops but pretending to be sooo grateful for the top from C&A (what ever happened to C&A..?) thats he got for me.