When there is such a shortage of information on the internet about an artist, like in the case of 雨宮麻末子, is very likely that someone has made a mistake (incorrect transcriptions, misprints, and so on). It's perfectly understandable, above all in this case, because the difference is almost imperceptible to the naked eye. 雨宮 麻未子 is this artist real name (末 ≠ 未).
Here you can see a sort of profile page for 雨宮 麻未子 and
this is her twitter (Mamiko Amemiya is her romanized name).
About 大野雅子, in
this website there is a little of information about her and if you click on her photo, you'll go to her
personal blog where she reveals her given name is Masako. Apparently there's nothing one can do to find out her family name, but lucky for all of us, I don't give up easily and look at what I found:
Ta-Da! (Masako Oono would be her complete name, Kurahashi was her maiden name, you can check that
here).