The s position can be defensive or feeding pose. Even if she doesnt want to eat it she will still be defensive.

There are some female ball pythons that eat great to 900 or so grams then get finicky and go on and off feed intermitantly. Maybe its the finicky teenage years i dont know but it I have heard about it from several folks and had it happen to me as well. Now most of my girls dont do this but it seems to happen sometimes and around that size/age.

Sounds like you got one of those, just be patient, she will be fine, in her own time.