My Doctor also prescribed this to me when I was 3 months postpartum. Unfortunately within a few weeks of me using the medicine, my milk began to dry up. This is a known side affect of using this drug, and I would caution her use of it unless she is prepared to stop breastfeeding.
I went to see a Lactation Consultant to help me bring my supply back, but it wasn't an easy road. Luckily my son is now 7 months and we are still happily breastfeeding, but that was quite a scare. Breastfeeding is extremely important to me and I plan to breastfeed for at least a year.
Sorry I can't give any other recommendations for her, but I thought it was important that I warn you about my experience with Premarin.
One last thing, Premarin is made from the urine of pregnant mares who are treated very poorly. They get no exercise, have reduced water consumption (makes the urine more concentrated) for six months. Animal cruelty is a huge issue for me, and had I known any of this before taking the cream, I never would have.