examined. Maybe it's just you feeling responsible somehow. I have to assume you are a perfectly normal person, so that's how I'm gonna roll with this.
Could be your girlfriend has some diarrhea, you kinda get that feeling like the end of the digestive tract is just dribbling and carrying on, when it's just plain old ordinary diarrhea. Particularly since your girlfriend has gastrititis, she's more likely to have all kinds of crazy indigestion
doc or the local county free clinic and they can see if she has a run-of-the-mill gastro infection, which antibiotics get rid of that. They can also give her antidiarrheal medicines, too. Or she can go to the drugstore and get some over-the-counter antidiarrheal medicine herself and give it a go. But if she continues to have indigestion, she should go to a doc, everybody gets bacteria in their gut now and then, like food poisoning or stomach flu type stuff, where medicine is needed to kill it off.
Also, diarrhea will make the rear feel sore, too, so she can put some lotion on there after she bathes, and it will soothe it, but plain KY jelly in the blue and white tube at the drugstore is really the best daily lubricant until she gets the diarrhea under control. One thing that helps diarrhea that isn't caused by some bacteria is to do the three things necessary for regular digestion: Drink plenty of water, get enough regular exercise, and eat enough fiber foods (like oat cereal, whole grain sandwiches, green leafy vegies, salads).