My Mother In Law Is 89 Yrs Old, With 4th-5th

My mother in law is 89 yrs old, with 4th-5th stage dementia. I love her dearly. Constipation is a problem due to inability to use stool softener much because she will not take in enough fluids. How can we curb her issue?
Also what does clear foamy vomit tell us?
My apology 4 asking u. I do not own a credit card. I will not use hers. Again, my apology.