Hello there.... My dd did exactly the same at the same age. As I know EBM tastes sweet than some Formulas so until I tried second stage formula that tastes better and has different nutrients she took it. I also tries solids with milk and she identify the taste!!!! She is taking now SMA Promil, I am not sure if you have it, but you should try with second stage and do as suggested with combining both at first and then less and less until she likes the taste. Hope this helps...
Good Luck.