Hello, and welcome to the boards
It's unlikely that the df will work straight away. Your lo doesn't know that she is supposed to sleep through the night. What the df does is top her up to go for a longer sleep, so, when she wakes a few hours later, you can be confident that she is not waking out of hunger, but habit. This gives you the foundation to break this habit, and getting her back to sleep. Once you have done this a few times, then she will stop waking so often at night. You do need to do this a few times, though, and be consistent with it.
Good luck