Oh I already told her she or her Mom should send me a picture of her newly decorated room! We live six hrs away from them so I can't take her shopping myself.
I haven't decided how much to send yet, but I usually buy her a gift that's no more than 50.00. (But it depends on the gift - I broke this rule with my nephew last year, I wanted to get him a telescope, and the least expensive one with good reviews on amazon was 65.00.)
My sis will decorate the room for her, too, but I agree NyaChan, if it were my DD I wouldn't ask others to help fund it as a birthday gift. I've never done this with my own DD, but if she wanted her room decorated and I didn't want to otherwise, I might tell her that her Dad and I would redecorate it as her gift. I wouldn't ask anyone else to help fund improvements to my own house - unless they offered or really, really wanted to.
My sister is kinda cheap this way. They are fairly comfortable, financially. They can totally afford to re-do the room themselves. I guess that's another reason why it aggravates me. (Off-topic but an example of how cheap my sister and BIL are - they re-did their kitchen a few years ago, and my Mom and Dad, who are on a tight budget and retired, asked if they could have the old cabinets for their own kitchen, Said cabinets were about 3o years old. Sis and BIL said No, but offered to sell them to my parents for way more than they were worth, imho. My parents then declined - my Dad could have (and later did) bought new cabinets for what S and BIL wanted for the old ones! So - S and BIL threw the old ones out when they remodeled. I realize it's their prerogative to sell their old cabinets if they want, but just telling this to demonstrate they would rather throw something out than give it away to someone, even family. My parents were completely confounded by the whole thing and even a little hurt. But I digress, sorry....)
My sister will also call my brother and myself and say she's found some expensive item to gift to my parents for Christmas or a birthday, and she'll just buy it and we can chip in, okay? Um, no. A couple of times I've agreed, but most of the time I've already planned to get them something else, and declined. She's learned to stop trying to talk me into it. One reason I don't like it is because the only thing I would have had to do with the gift is paying for it. I want to gift things that I actually put some thought into, myself.
So it is with the niece's gift. Apparently, though, niece does want her room decorated enough to call me and ask to help out, so I will.