No, you're not crazy, you care about your daughter.
You might be interested to see other causes of stretch marks here:
http://www.mayoclinic.com/health/stretch-marks/DS01081/DSECTION=causes
And consider whether if cortisol testing is repeatedly fine, whether she might have something else.
For example, take a look at this on Medhelp in regards to Marfan syndrome:
http://www.medhelp.org/posts/Migraines--Headaches/Marfan-syndrome-whats-it-to-do-with-headaches/show/1233784
And according to medicinenet, many who have Marfan syndrome exhibit skin stretch marks, even with no weight change. They are also slender.
http://www.medicinenet.com/marfan_syndrome/page2.htm#what_are_the_symptoms_of_marfan_syndrome
And another cause Mayo Clinic lists for stretch marks is Ehlers-Danlos syndrome. The National Institute of Health indicates headache can be a symptom of it as well:
http://www.ncbi.nlm.nih.gov/pubmed/10595288
So, what you may need to do is keep searching for answers for your daughter and advocating for her. Keep hunting!
I hope too that since they think your daughter's pituitary is enlarged they plan to follow up with regular dynamically done pituitary MRIs with and without contrast to keep on eye on things there.