B.,
My son was having the same issue also. He is 8 months. I called the doctor and they recommended apple juice. They said that babies can have 1oz per every month of age, so since my son is 8 months, he can have 8oz. I did this for one day and he went perfectly. Then I went back to watering it down, and he started to become constipated again. So I gave it to him for a few days and it helped, however he started getting a slight diaper rash, so I give him about 70% apple juice and 30% water, it's working great. I have also been giving him yogurt, which I heard helps with constipation and that is working well too. However, your daughter may be too young to eat yogurt so you'll have to check with the doctor.
I did have this problem a few months back when he first started solids. I had a different pediatrician at the time and they recommended karo syrup, but I did some reading up on it and I decided against it. They say there is a risk of botulism.
As far as jar foods go, sweet potatoes, prunes, pears, apples, bluberries, are all good foods with fiber. Just remember the three day rule.
Good luck, I hope you have a happy pooper soon!