Hello, I'm a mom of 3 girls and hopefully I can help with home remedies.
To soften the stools naturally: If she is drinking out of a bottle/still nursing, you can put light Karo Sryup about 2 tbsp. full in her milk., or try the pharmacies for correct dosage for PEROCOLACE. It also works very well.
For a natural laxative for babies: Open a can of 7-up and let it get flat(no fizz), then also put it in her milk. It really works also.
The last resort, you need to go baby suppositories and deal with her that way. Once she has gotten unstopped, keep doing the natural remedies daily.
One of the big reasons that a baby gets constipated is she's not drinking enough water. If she's anythink like my girls, she hates water. So, any drink that I could get away with, I used to water to dilute a coke, juice, sometimes I put water in their milk.
I hope some of these remedies can help. But for sure do not be afraid to use the baby suppositories.