Pain in this area, especially when in conjunction with a fever, is potentially
appendicitis, which can be deadly if allowed to
burst. The pain can radiate toward the belly button, as well.
If it's not in this area, it's up to you if you take her to the ER, though it might not be a bad idea. At the very least, be there for her, get her what she needs, help her around if she needs to get to another room in the house.