Iwadou Seiko 岩井堂聖子(いわいどうせいこ), known under the stage name Takahashi Mai 高橋 真唯(たかはし まい) was born in 1984 or so the Japanese wikipedia says.
So I doubt she's the same as the Takahashi Mai 高橋まい I think you're refering to tho she's listed as born in 1996 so probably not a junior idol anymore?