I’m so sorry about this young mom’s difficulties, @oregon101. I think the single most important element in the early weeks and months of mothering is that the mother enjoys and is comfortable with her baby. I was a LLL leader for many years as well (never thought I’d say that on CC), and I support breastfeeding, but not when the mom is unhappy about it and either doesn’t choose nursing or sincerely doesn’t want to continue. If your D2 doesn’t want to continue, I think she should be encouraged to follow her heart. Perhaps she’d be willing to continue pumping and feeding a combination of formula and breastmilk? She can also put the baby to the breast for contact, comfort, and nutrition while supplementing - there’s certainly value in that.
I’m surprised to find that no medical professionals have focused on the baby’s slow weight gain. That suggests to me that it might be within normal limits, since it’s hard - around here, anyway - to find MDs/NPs who wouldn’t be recommending supplementation, frequent weigh-ins, and even weaning if the weight gain is inadequate. Perhaps they feel that it can improve with the right management? But if the mom is exhausted, feeling inadequate and sad, and just wants to feel in control of the situation - again, I think she should be supported in following her heart.
She’s lucky to have you in her corner. I hope things work out well for her.