I love Sonia!! I pronounce is SAWN-ya (sawn rhymes with yawn). I've also heard it said SOHN-ya (sohn rhymes with lone). The second pronunciation sounds a litlte pretentious to me, but I could like that one too I think.
Sonia seems like she's usually a down-to-earth friendly girl, but can certainly have a flair for the ridiculous and unpredictable at times. A great mix!