Well, the Internet came to the rescue. I googled & I asked you on my facebook page, and eventually I discovered how to get ink out of wall decals.
Based on my experience, here's what I can tell you:
1. Do not use magic eraser (I tried- it didn't work, so I pressed harder, then I saw the colour coming out of the sticker. However, the magic eraser always works wonders on our ikea mammut kid sized table- and you better believe I've had to use it many a time ;)
2. Do not use Vim. (I find that Vim works for a lot of things, but not wall stickers- it'll take the colour out)
3. Do not use a cloth with soap. (well you could try it- it didn't take the colour out. But it won't take the pen out either)
4. DO use Rubbing Alcohol! (It really works & it doesn't mess with the colour of the vinyl.)
5. Depending on how hard your little artist pressed with her pen, you may be left with some colour & an indent on your stickers, but they'll look a lot better than they did right after she finished her work.
6. I am told that Goo Be Gone spray gel will also do the trick. And I even heard someone suggest milk on a cloth... has anyone ever tried that? Sounds strange to me.
Now, please tell me.... does anyone know how to get pen off of a painted wall, without taking the paint off? Cuz that little bit you see in the picture isn't all I'm working with ;)