The only Non-drug (besides local) I can think of is acupuncture. This would probably require the acupuncturist going to the dentist's office. I don't know of one who will do this, nor the fee if you find one.
Plus I don't know how you child would handle the needles in general.
I agree with Vitamin C, but not fish oil at this age. You can find however non-fish DHA (spectrum)- but what she needs if EPA for healing. Check with the health food store.
Formula/milk is not always the cause. Genetics can play a role. If you live in Pasco County- the water if not flourinated. You may need to get you child on Flouride vitamins depending on the county you live in.
Start brushing- if if you haven't already. Tom's of Maine & Earth's best have flouride free tooth paste for children under 3 yr.
My daughter was formula feed- age 3, not the first cavity. On Flouride vitamins, but she doesn't brush well (often won't let us without a knock down drag out fight.
Age teeth come in are also a factor- later the come in the better- less exposure to germs, sugars etc.
You may want to consider having her teeth sealed when she is old enough.
You may have no choice but to sedate- for the safety of your child & less stress. Have the dentist explain all of the risks.