You don't need anything for this project other than the shirt and the matching thread!
First deconstruction. Lay your shirt out and cut down the inside of the armpit seams and down the sides. Set your scraps aside and save them for later.
We need to make the neckline a bit smaller. So we'll cut across the shoulder seam. Then pull the front of the shirt up (or back of the shirt down) so that that seems around the collar match up. Take it up or down as much as you need. Pin and stitch. I double stitched instead of surging through this project because it is NOT fun to serge knit!
Now flip this little apron thing over your babe and mark where it hits the edge of her shoulder. I just used my scissors and snipped it because Hailey gets kind of scared when I start pinning. Lets just say she's been pricked a couple times when taking the garment off. Woops!
Now use this measurement as a guideline and snip around the armpit. you can measure and mark but I just eyeballed it.
So we will now re-attach the sleeves. Go back to those scraps you cut before and carefully remove the sleeve by cutting the seam off of it. Making sure to cut just inside of the seam, you dont want to take alot off at all. Then fold in half to find the middle and match the middle up with the top shoulder seam. Start in the middle and pin down each side matching the edge up. Make sure you have right sides together. Finally stitch them down again starting at the middle and working your way down each side.
Now grab a shirt that fits your child and use it as a guideline match it up to the one you just stitched in place. Mark it either with a disappearing ink pen or a regular old pencil (it'll wash out, promise).
Then draw a line down to the bottom of the shirt. I just wanted to do an A-line dress but if you wanted it to be more fitted you definitely could make it as fitted as you like! Pin in place and stitch. At this point I trimmed the selvage and snipped the armpits so that they would turn out nicely. My bottom hem didn't match up for whatever reason (I think probably because I messed with the neckline?) so I cut it off and folded a bit under. Then double stitched it in place with a light purple thread that went well with the flowers on the shirt.
Finally I added some decorative stitching to the sleeves and neckline. But this is totally optional. I think it funked it up a bit which I really love on my little pumpkin!
Pop it on your patiently waiting little girl and go play!