You may be able to make a deal with your Mom that if she can get you the LE doll of the years, and maybe an extra outfit, you'll handle the rest.
My fiance and I have a deal set up that is kind of similar. As of right now (until my collection gets too big) I get a doll for my birthday and one for Christmas. If I want another one any time between then (from December to September) I have to buy it wiht my own money which means money I have made from my sewing and ebay (my paycheck from work goes towards bills and such). But since he got a PDA and a DVD set for his birthday, my bithday spending limit went a little higher so I got a used PM Samantha and Jess (who should be here any minute now).
Good luck and let us know what happens.

-Jenifer