Based on the information it seems like you daughter is having stomach pain, a clay colored stool and more over you gave her Gaviscon
and worried about she having some issues about it.
1) Gaviscon do not have major issues if given to child, its only heart burn medication.
2) The stomach pain and the clay color stool gives a red flag indication of having some issue with liver/gall badder.
3) Please take her to near by internal medication physician as soon as possible. Please take it seriously and get her checked.
Hope it helps.