Hello Aelita!
Wow, it looks like in this first row, the last size (14) was left off on the st counts. Thus, this should be added (in blue). The 3T size should have 27 for a st count, not 25, and that is (corrected in blue). Adding in the size 14 should now make the size 9/10 right. The size 9/10 you chain 32, and have a st count of 31. So this should work as written.
INCORRECT
Row 1: Ch 22 (24, 26) |♥| 26 (28, 28, 30) |♥| 30 (32, 36), sc in 2nd ch from hook and in each ch across, mark this as RS, turn––21 (23, 25) |♥| 25 (25, 27, 29) |♥| 29 (31, 35, 37) sc
CORRECTED
Row 1: Ch 22 (24, 26) |♥| 26 (28, 28, 30) |♥| 30 (32, 36), sc in 2nd ch from hook and in each ch across, mark this as RS, turn––21 (23, 25) |♥| 25 (27, 27, 29) |♥| 29 (31, 35, 37, 38) sc
I am so sorry for these errors. I am so surprised this pattern has been release so long, and you are the first to bring this up. THANK you so much Aelita! Again, I am very sorry for these issues! Please let me know how everything is with these corrections
PS, the 14 yr old should fit fine. When you get the the waist, there are notes for making the ribbon band lower, in case she is developing. If she is in a training bra, this dropped ribbon row will be more comfortable on her.