Well, is she eating the soil, or just digging in it? It *could* be a chemical imbalance that makes her wants dirt. Maybe after she gets on the right supplements she will stop digging. I honestly have no idea why she is digging.
Per the supplement, you can use a multivitamin with D3 in it and only use it twice a month, and all your other feeding can be the calcium without D3.
I use reptivite with D3.
So my schedule is calcium without D3 every feeding, but the 1st and 15th I use reptivite with D3.
That cuts out one of the supplements and makes it easier, IMO.