Doesn't happen where I live. Here,
Sara and
Sarah shorten to Sarie (SAHri). Serah doesn't happen either, though an Afrikaans person speaking English would typically pronounce
Sarah as Serah.
I'm with Manipura - the only form of
Sarah I like is
Sally. My dad wanted me to be
Sarah Anne after his mother, and I'm very glad it didn't happen. I could see myself as
Sally all right.