Mesenteric adenitis in child - How long will pain last??

How long does mesenteric adenitis pain last???? My 8 year old likely has this and has been in pain for 4 weeks, unable to go to school. One doc said it should have resolved within 2 weeks (so the pain must be in her head) and another doc told me it could take up to 6 weeks. I feel so badly for her and just want this to go away.