Is there any harm in having her tested, just to make sure? Crohns can be very destructive so a good thing to at least rule out or have a baseline result so, if the problems continue and more scans are needed, any change can be measured.
What blood tests out of interest? Inflammatory markers maybe? I know that blood tests can help diagnose things like Coeliac but I've been tested for Crohns (or other things) and, albeit I'm an adult, have had all kinds of scans including camera ones, MRI and a barium meal. They have find signs of inflammation in a stool sample too I think.
I've read that Crohns can often make people not want to eat due to the symptoms which can cause weight loss as well as complications from the disease itself. I believe it's common but not definitive.