Thank you for your query,
Nothing to worry.
Pooping 4 to 5 times in a 4 months old child is quite normal.
Continue exculsive breatfeeding till the age of 6 months and the frequent passage of stool is due to a gastrocoloic reflex and it is normal.
Fontanelle will be usually low from the suraface and it will raise intermittently during crying, lying position so nothing to worry.
As her feeding is normal, happy and activity is normal , there is no reason for the dehydration
and no need for worry.
you can apply lotions like calosoft or dermadew caloe, if not subsided consult your Pediatrician
Hope I have answered your query.