As per your explanation I realize she has extrem pain in stomach and towards lower
rib cage. Now if there is pain that means there is something wrong. Here you have also told you have done
ultrasound abdomen and have tried with various things but still she has no relief.
I suggest to take new ultrasound scan of her abdomen. And check report what it says. If there is any new diagnosis then take treatment as per that. But if there is normal report then I will suggest my patient to do lifestyle changes first.
That is food habits like have break fast well, lunch average and dinner minimum maximum by 8:pm or before that. Do not have any thing after that. Maintain same time for daily break fast, lunch and dinner. Apart from this I suggest to have different fruits and vegitables. Take fibre rich diet. Have enough amount (3-4liter)of water in a day. Sleep well, do regular exercise like walking for at least 15 -20 minutes.
Above all are basic advice given for digestive system problem.
Now to answer your question: here you have ask what could be the cause for lower rib cage pain?
Let me explain you here we can just assume, it can be weakness of lower ribs, it can be due to gall
bladder stone, it can also be due to acidity, as well can be due to gastric ulcer.
Here what ever will be the cause first we need to diagnose with ultrasound newly perform one. And them.take appropriate needed treatment. Apart from this the basic changes in life style and food habits are must.
I am sure this must be useful for you. Try it and take care.