It’s a fairly common pronunciation error, and I wouldn’t worry about it at all. Nor would I try to do anything about it just now. The main language goal for the 2’s is to let her find joy in talking and communicating. You are fortunate that the “f” sound is one that is produced by the external articulators; look in the mirror and make the sound, and you will immediately see what I mean. (The “f” and “v” sounds are made in exactly the same way. The only difference is that the “v” has voice with it and the “f” is made with the breath only.) When your daughter is a little older (not before 3½), play some games with her and have her make the sound for herself. After she can make the sound (probably spewing saliva all over you), you can continue the game with a word, prolonging the “f” sound—“ffffffish.” But I predict she will have corrected by it herself before then. Remember to praise her when she gets it right.
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