Is she eating treats or people food and keeping that down?
Is she keeping water down?
Is she defacating (#2)?
It is a very good sign that she is eating and drinking and keeping that down. From my experience, when dogs have a complete obstruction they become very depressed. If they attempt to eat or drink anything it comes right back up. After 48-72 hours of being obstructed they are extremely ill and dehydrated and will not eat anything.
It sounds like she is stable for the moment. As long as things are going in, moving through, and coming out, that is good.
She may just have irritated her gastrointestinal tract by eating that bag. If she does not get back to her normal self in a few days, or gets worse, then she needs to get x rays in case she has foreign body.
So, for the next 2-3 days feed her a bland diet of boiled white rice and either boiled hamburger with no fat or plain chicken as a protein source.
Give her peptobismal at a dose of 1cc per pund of body weight every 8 hours. There are 5cc in 1 teaspoon.
This should have her back to normal in 48 hours. :)