How do I convince my mom to let me upgrade my handheld videogame system from a Nintendo DS to a SP?

I have an SP with Wario Ware and Fire Emblem, and she says I should but the other games used and get my play out of the SP. The only problem is that I really wanted a DS, when I heard the rumor in 2003, but my mom got me an SP instead. I know it was a nice thing to do, but I have had my SP for 4 years now and think I am ready to upgrade.