My DS's words were exactly the same as your DD's. He is 5 now and still doesn't pronounce 'th' so will still say 'somfing'.....but I'm not too worried. Not long ago he couldn't pronounce 'r' or 'g' or 'c' 'k' but one day it just clicked. I would show him where in my mouth my tongue went when saying the sounds and over time he got there.