It would depend on where in the ileum it is located but if it was close to the ileocecal valve that connects the large and small bowel then a scope might reach for a biopsy.
There is also a pill cam which would allow them to see the inside of the small bowel but no biopsies.
There is a blood test, the Prometheus test, which ins may not cover that can give some indication but it is not fool proof.
Since those with CD may have to have many imaging tests, some GIs opt for MRE(magnetic resonance enterography) since it doesn't use radiation and is very good at visualizing the small bowel.
It can take some time for budenside to work, linger than with pred. If her blood work is a good indicator of inflammation(inflammatory marker like CRP) then regular testing can give you some idea of how effective the med is. If not, a fecal calprotectin stool test is a good indicator for some.
My son's disease was located in the terminal ileum around the ileocecal valve. At time of dx he had pain, joint pain, mouth ulcers but not so much D. Due to the severity of his disease he was placed on remicade straight away.
A lot of us parents keep symptom journals or food diaries to eliminate foods that may be a culprit. Also, begin making a list of your concerns and questions so that when your daughter goes to the GI she can have those in front of her and direct the appointment towards her/your biggest concerns.
There are other things that could cause inflammation, some more serious like cancer others due to things like overuse of NSAID medications, intestinal TB. But of those, most likely for a young person not treating injury or arthritis CD would probably stand out the most, kwim?
Good luck.