Found out who
she is. It's Chikako Kamatani apparently. Uwabo told a friend who told me she may be "Ms. Kamatani". Then I did a little research and found a Chikako Kamatani who did sound design for
Pinobee: Wings of Adventure.
Then
right here on VGMdb, I see a Chikako Kamatani credited along with NAV, who Tarnya worked with on
Phantasy Star II. I'm trying to confirm it, but it sure does look like that's her full name. Another SEGA mystery solved, hopefully.
EDIT: Takayuki Nakamura confirmed it.