As well the adult Oxbow goes over much better then the baby rat food. The store I order from accidentally ordered baby block and my guys refused to eat it unless forced to...we also had some living world hamster extrusion which they enjoy. I would treat them with a bit of duck, egg or chicken to make up for some protien.
The seed mix would be like feeding a child lucky charms and then feeding them cheerios...they are obviously going to want the lucky charms back even though cheerios still taste ok and are good for them.
Just will take time to make her feel the same and I will highly bet that when she gets a taste of the adult block she will eat it.