I'm assuming this is just something she will grow out of, but my DD3 has started to speak with a speech impediment that she didn't have before. As far as I can work out she is mimicing her key working who has a similar speech impediment. It's just started in the last few weeks so there is no physical reason for it. DD is kind of a law unto herself anyway as she has a strong English accent even though we live in the heart of Scotland and all have Scottish accents 
I'm assuming she'll grow out of it as time goes on? Anyone have a similar experience?
My older DC (6) has also changed his speech since he started school and now pronounces certain words differently. 
I have heard before it's a sign of having a 'musical ear' to copy the speech patterns etc of others. Don't know whether that's true or not!