Confused on my girl feeding

ok so before you read anything my husbandry is fine because she only does this like once a month or every other month.

Okay so my biggest girl, shes like 3300 grams, so she could easily eat a medium rat. Which is what she use to eat, but ever since I got her back from my ex she has like lost all of her confidence. She will only eat small rats, which is fine, but like once a month or every other month she will kill the rat then start to eat it and get to the shoulders and then just give up like she thinks she can not get her mouth around it. Then she just spits it out and then well I end up throwing the rat away. Has anyone else had this happen to them? Like I said her husbandry is perfectly fine, and I would be more concerned if she did this every time but its only every once and while. She also will eat mice but she prefers rats. I get my rats from the same place that I always do so its not like the rats are bad or anything but mainly I am just wondering if anyone else has had this issue before.