We used Lactaid drops for a year treating our son's whole milk to
eliminate lactose since we were told he was lactose intolerant (turned
out he was allergic instead.)

We used to get the drops at Giant Groceries in our area. You need to do a
trial to figure out the right amount she needs. We started with 30 drops
per gallon and had it tapered down to 10 drops/gallon near the end.

Has the doctor suggested milk with acidophilis  added? It might help
rebalance her gastrointestinal beasties which can help with the enzyme
production.

Good Luck,

Cindy B.