To ask for medical advice

This is not the place for medical advice.

You have no idea who is answering you - some will be honest about who they are, others will not.

If you have concerns go back to your GP. If they have said they are normal, why are you questioning this? You can ask for a second opinion if you have reason to distrust the original GP - most services will have another one you can speak to.

I'm not a clinician. Extensive experience of bowel problems and pursuing investigation.

GP will tell you that level of ferritin ( iron storage marker) is fine. I'm on an iron protocol group onFB and they heavily criticise current markers used for most nutrients including ferritin levels. Most would say this isn't optimal at all. This level might indicate an issue from heavy periods to malabsorption or just diet low in iron. Trying to raise iron levels would be the first thing advised - whilst secondly looking at issues impacting ( e.g possibly the stomach problem).

There's a raft of roads you can go down regards the bowels. If it has been going on a long time now and not getting anywhere, I'd look at further investigation. Some is invasive though.

First thing might be requesting a stool sample - GP can process I think and they test stool for inflammation levels ( feacal calprotectin)

An MRI can be requested, with contrast to look for bowel inflammation or structural issue like diverticulitis.

Next stage might be a colonoscopy - bit invasive but they can take small samples ( biopsies).

If this is a problem of motility ( bowels moving too fast or slow) it won't show on an MRI or stool sample. It can be very painful though. A swallow camera pil is excellent for measuring speed of transit and it takes photos all the way through. You then poo it out. You have to push for this usually as if the above are all normal they will often go down the ' anxiety' road, particularly with young women.

I went through all this. Everything normal then I pushed for a camera pill test , ended up doing it privately. That did show exceptionally fast motility as a result of Autonomic dysfunction. I also have Ehlers Danlos Syndrome which impacts how the bowels move food through.

Other possible areas for investigation could be allergies/ sensitivity. I think the tests for this aren't that accurate though. If willing, trying dairy and gluten free for a while might really help.

Some people try antihistamines for the gut to see if it is an excess histamine problem - famotidine is an H1 blocking antihistamine that might be worth a try.

Again it all depends how bad things are,how long it's been going on. It's worth investigating based on low ferritin though.

4 things to raise with GP. Could it be…..
Low iron stores
GERD
Gastroparesis
Chronic appendicitis, (rare but I had it as a teen and it took 4 years of going back and forth to the GP to finally have it removed), though with no vomiting it’s probably not this tbh.

There's good advice below in relation to blood and stool tests that should have been done to exclude other causes, & other considerations, e.g. diet, anxiety.

https://cks.nice.org.uk/topics/irritable-bowel-syndrome/

The ferritin concentration suggests your daughter's iron stores are low, consider her diet, & her menstrual flow, if other tests are within range/negative. There's some evidence that ferritin levels at the low end of the range should be treated with iron supplements to raise levels to a minimum of 50-70

https://www.bda.uk.com/resource/iron-rich-foods-iron-deficiency.html

Is the pain always there? Or are they like episodes that come on and then abate? If it’s episodes, how long do they last roughly? Are there other associated symptoms like nausea / vomiting etc when the pain is there? What does the pain feel like? I.e. sharp, achy, stabbing etc?

Is she vomiting OP?

coeliac? the tests would be IGA TTG tests if they'd been done as part of the bloods.