help!!

I know this is for periods and stuff like that but I'm hoping some moms can help me out. My friends baby is constipated. She's only 4 months old but she's chewing on EVERYTHING. Could the constipation be associated with teething? Is she too young to be teething? Nothing in her diet has changed and she's getting super fussy (which is not normal for this happy baby). How can we help this poor sweet baby poop??