Cute, but ultimately pointless.
Personal opinion on what could improve the idea:
1. Full character customization.
-Or at the very least do a menu select for all the underwear and accessory options, have mercy on people's mice.
-For now, you wouldn't even need to add thousands of parts, just make it possible to mix and match the assets you already have
-RGB/HSV colour picker for hair/eyes/skin/clothes if possible
2. Genuine interactivity
-Sorry, but the dumb "point my finger at your cursor" thing is one, pretty useless/awkward, and two, very buggy. Now, the idea itself isn't terrible, but you would need to actually animate the character to act like she's looking at the mouse, and not just glue the fingertip to the mouse cursor. Preferably, the final result would be a natural breathing idle, with both her eyes and her head following the cursor while blinking etc.
-What Regnak said is a cool idea. Make her react to whatever you are doing on your PC. Have her walk around the desktop, act like she's looking at whatever you're doing on the screen, maybe sit down when you're watching a video. It could be invasive, but at least there would be some sort of point to it. Make it possible to poke her, headpat her, maybe tickle her or stimulate her, then get her to react to it in some way. Maybe she occasionally (would have to be pretty rare in order to not become annoying) she tries catching your cursor, and you need to flick her forehead to make her calm down or something. Or she moves out of the way when you click on an icon that's behind her.
-If you want to be fancy, having multiple personalities, each acting slightly different would make it exponentially better.
-If you want to be
REALLY fancy, programming her to have some actual functionality would also widen your target audience. Sort of like a desktop assistant. I do realize, of course, that making her actually have a dialogue with you isn't really feasible yet (AI tech isn't quite there yet), but reacting to simple commands that could be preprogrammed I believe should be doable, for example
You type in "Run GAME_NAME for me" in a dialogue box
She responds with "Sorry, I don't know where it is - could you show me the file?" - and you can then open a window to pick a specific .exe file. After you do that, she automatically runs that *.exe file every time you tell her to run that specific name.
Basically make use of the technology and make her into a sort of interactive desktop pet/assistant, instead of a limited 3D desktop figure that's just... there.
I can't help but feel that as it is, it's just a fancy resource hog that could be easily replaced by doing a screenshot in Koikatsu/CM3D2 character editor and pasting a transparent image onto your wallpaper. Or even simpler - by a nice wallpaper.
Then again, maybe I'm just not your target audience. I used to like this kind of shit when I was 14, now... Unless there's some actual interactivity to it, I really don't care about it at all.
Of course, I do realize that this would be incomparably more complicated, but like I said - it's just my personal opinion on what would make it more interesting.
Also, I'm not a programmer, so I don't know how difficult all of that would be (I imagine making the animations would be either the second biggest if not THE biggest hurdle), but I tried keeping it down to Earth... At least I hope I did