Ok, You Want It, You Get It!

Actually, I'm liking this.
Since you say this is your first finished piece, I'm going to assume that you have practiced already quite a bit.
I also wish to address the mouse bit. I think you should really consider moving up to a decent quality tablet. I think with a little time you could easily grind this in to the mud.

Ok on to actually critiquing the piece..... just a sec.... had to get a drink of my soda..... and good....
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holy shit.. I'm actually doing this right, I'm actually making a proper list of things to discuss........
this might take a moment....

ok.. Although I may have a lot more that I don't like on this than I do, don't take it as a bad thing.

Don't like
To be honest I find that I don't like the size of the eyes. they bother me a bit. If you could take them down a bit I think that would add a little more appeal to this over all.

For some reason I think she is dirty. Not in some sort of racial or sexist way, but as in it looks like she has dirt on her. Did you use the Burn tool to make her shadows? If so, ouch.... you should try it another way or smooth it out quite a bit.

Moving on, I find the background pretty bad. although I can understand that is was just a background I find the color a little strong and could be desaturated a bit. Also I think that the color should be altered a bit since it seems to be in the same ball park as the clothing color, perhaps some compliment color of either the hair or the clothing to help pop the out a little.
Speaking of the shirt I think a little more time would have helped. To keep from getting ahead of my self I'm going to discuss it better in a moment.

The lighting is something I want to really touch on because in some areas I'm ok with it, and in others I think needs some improvement. The Shirt is where I will start. I think some more harsh shadows and some darker areas would have helped. I can see where you started to push it, but it seems you got a little scared of ruining the whole thing and then backed off. I say to hell with the fear, and drive that hammer home like John Henry working for some Fried Chicken and some water melon! (Bad Joke I know.... :P I lol'd....)
The next lighting bit relates to the last one a tad since I am going to suggest that you push out your highlights on the hair and earring a bit more to the strong side. This should give a bit more of a glossy look to the hair and earring. Similar Highlights should go on the button of the blouse. Just to give it that high sheen that plastic things seem to have. Higher highlights will also help the shadows seem more deeper. And lets not forget, even if you screw up, there is always the undo button.

As for some likes. I do enjoy the earrings. I think they are good, but they are also pretty small. It's sad that you do not have a larger version of this so that I could see them in better detail.
I would like to mention that you work in a larger, print ready, size. I know this will mean that they take up a little more space, but when you upload them we'll get a good look at all the minor details when we get that high resolution brought up.

The gloss on the lips is kind of nice as well.

One thing I am on the fence with is the facial structure. It seems a little exaggerated with the cheek bones and the chin. Although they are still with in acceptable parameters. Again I think a lot of it comes down to the lighting.
Google some subtle lighting tutorials.

4/5 (if you were in the portal.)
7/10