Agreed with the others, I really really like the jacket idea. It's very cute.
However, it doesn't really match the rest of the design. Like, this is just my own personal opinion, but I feel like her entire outfit is very mismatched? The jacket has a lot going on, but the shirt is dreadfully plain, and the bottom half is very uninteresting. Again, I don't mean that in a mean way or anything, so I hope you don't get offended!
Personally, I tend to dislike stripy black/another colour socks in designs because I feel they look cheap, so if I were you I would change that somehow. The belt with the heart also looks pretty cheap imho.
What I think you should do is research what type of clothes/clothes shapes work well with that style of jacket.
For example, if I was you, I would not have a short sleeve t-shirt with that jacket as it feels really exposed because of the shorts? I'd make her t-shirt long sleeved, that way it balances out. I think that clothes shape would look nice.
If I was you though, I'd completely scrap the bottom half because I don't think it's particularly eye catching and the top would have a good potential, so try to match it?
If you're short for ideas, then research fashion or even play dress up games to give you some inspiration. It might not seem like it, but I've found that's the best way to try and think of original designs.
Here's a good website:
http://lookbook.nu/ I use for fashion because personally I think the fashion on that website is very nice. But, it's all up to you. Just research and I'm sure you'll get inspired by something.
Hope that helps!!