She and a few other female vocalists were part of what can be called "Metal Idols/Kayo Metal Idols"; a short lived phenomenon (around 1982 - 1987) where some producers just wanted try a heavier sound with the then popular kayo idols.
Heavy Metal was on the rise in Japan with bands like Loudness, 44 Magnum, Vow Wow... so it's easy to see they just wanted to capitalized on it.
But they did not forecast the band boom which started 1984 - 1985 and embraced all genre including rock (from soft rock to hard rock) even fronted by female vocalists (Rebecca, Personz, Princess Princess, Show-Ya, etc...). Heck, even "old-school idols" turned rock at that time (Ann Lewis, maybe the best example of all)...
As idols are pure producers' products, they disapeared as fast as they came. Only Hamada Mari "survived" from this phenomenon and still sings nowadays. You might wonder why. Easy: the "Metal Queen" was at least smarter than the other and starting her 3rd album she was already self-produced.
Other notable thing that happened thanks to this phenomenon; most sessions musicians that played in these albums started their own band (if it was not already the case): B'z, FENCE OF DEFENSE, MAKE-UP, etc... to name a few.
Also, if you like or are interested in "Metal Idols", I always point to this site as a good starter/reference:
http://matsnagger.ninja-mania.jp/Meg...megumisama.htm
http://matsnagger.ninja-mania.jp/jap...metaqueens.htm