My toddler's yaya has P-F syndrome. Now my daughter says phone as pone and fish as pish. Will this self-correct when she goes to school or should I keep correcting it now? So far I've been trying to undo it for a few days via repetition but it isn't working.

Give it time. My nephew also struggled with this when he was younger but when he started school, he managed to gradually get over it. I think they learn by repetition so just be patient and know that for many toddlers, it takes more than a few days before they pick up on things.