I laid out a pair of her pants on top of the pajama pants and realized I could probably keep the waistband intact and just take them in along the inseam.
So that's what I did. When she tried them on, they were still very baggy in the hips, so I had to take in the crotch seam from front to back. I lost the front tie in the process, so I made sure the elastic waist fit just right. I don't even understand why these pants had both elastic and a ribbon tie - weird. Then I hemmed them to the right length, and I was done.
They were a much better fit for my girl. I think she likes them!
Thanks for reading! -Amy