Hi I think it`s Jennifer Meyer. She a great friend of the star and I know Nicole Ritchie have one with the first letter of her daughter name. Check she have beautiful jewelry!!
I also think that it is Helen Ficalora...I have several of her alphabet charms (and a little dog paw print one too as well) and love them so much!! You can get yellow or white gold charms through her website (you have to place the order by phone, though) or you can get sterling silver charms from ShopBop.
I get stopped and asked about them all of the time.