Mila is having her first shed (since she is with me). That is incidentally one of the reason why I am not posting any pics yet..but..something is wrong.

It is the first time it happens to one of my snake, Thamnophis or others, and what happens is this: Mila, the garter female, started shedding this afternoon, and proceeded to remove the first inch and a half of old skin. Then stopped.
The skin looked not perfectly shed, did not have that "whole" look of all the previous sheds I have assisted to.....and in fact, after one hour of going around the enclosure, she managed to rip the shedded skin, and now she has her front half shed, and the bottom half unshed.
The rip is not even clearly seen...and the shedded skin is not whole, rather in two pieces.
The enclosure humidity looks right to me, there is one pothos, and one fairly large water dish....so what's wrong? What did I do wrong, or the seller, for that matter, and how can I correct the issue, if it is possible, even!

Thanks for any reply, I deeply appreciate advice and help.

Pg