Well it's clear she's overtraining - and there's no way to fix that except to back off.  Trying to run a marathon within such a short time of beginning to run is a pretty risky proposition. Cardiovascular fitness is only ONE aspect needed... and she's apparently got that one covered. What she may not have is the musculo-skeletal strength yet.  She should take this seriously and see someone for a definitive diagnosis - could be a sacroiliac joint issue, could be a muscle imbalance, could potentially be a pelvic stress fracture! Only way to diagnose this is to see someone face-to-face for an evaluation.  If she want to see a PT - send her to this page and tell her to use the links at the top of that page to search for a specialist PT in her geographic area.  I'd recommend the APTA specialist directory search engine.  Tell her to look for an Orthopedic Certified Specialist (OCS) PT and she can narrow her results further by selecting one that focuses their practice on lower back issues.  Depending on where you live, you may need a physician's referral - so she should probably see her doc first. Don't mess around with this - if she continues to run through the pain she's going to set herself back a lot further than if she just dealt with the injury quickly. 

Hope this helps - Janet

treat the cause, not just the symptoms... runningstrong