I can't really help but to suggest that...

a) it's probably nothing too serious / a strange habit she will get over / a sensation that she enjoys - MOST LIKELY OPTIONS

b) it could have a neurological basis and is worth watching and talking to yr GP / Pead about. Speech does come from several quite specific parts of the brain and can be affected without any other functioning being affected. Please don't be alarmed by me writing this. It's just a thought that comes from a Psych that tends to read 'psychy' things into everything!