Sandy Schwanekamp (???? - 2017) was a girlfriend of Zappa;
Frank had a blonde girlfriend named Sandy, at the time, and Dad didn't like her. That was clear, with no imagination necessary. I never could tell the reason. Probably just an Italian father thing. When Sandy came over, she and Frank would disappear into his bedroom.
Moved to Minnesota, in 1959 graduated from Saint Paul Central High School:
"Sandy Schwanekamp was one of Frank's earliest girl friends in Lancaster and I seem to recall that her parents didn't like Frank and that at some point they either moved or took her out of AVJUHS and put her into private school." 
Schwanekamp is included in the list of names on the cover of "Freak Out!" (1966)