Wow. Interesting suggestions.
Our daughter, too, has constipation issues that have developed into encopresis (intentionally withholding BMs). She developed this around 20 months, and it's still an issue many months later.
I'd advise you call the pediatrician's office and see what they recommend. We were specifically advised NOT to stimulate it on our own (because of the risk of tearing the tissue in the anus) and to bring her in for a nurse to do if needed. We were also advised to do all the fiber stuff to help get things going, and none of it worked for our daughter. But, it did for her older brother as a baby. So, if it's not working, your pediatrician can give you the best advice based upon her age.
When chemo gave me horrible constipation, I found senna to be my best ally (it's vegetable derived), but the pharmacist was not about to make a recommendation for our daughter as a baby despite the Ped's office being OK with it. So, she's on a capful of Miralax/day in her milk. She's also a big girl in the 90%+ on both height/weight, so her dosing may be different than another child of the same age.
I'm a big believer in calling the pediatrician when guidance is needed.
Good luck.