The Handmaid who is a member of the Mayday resistance is Ofglen. In the television series, the first Ofglen is Emily Malek, a former university professor who is assigned to shop with June. Emily quietly reveals that she is connected to Mayday, the underground resistance opposing Gilead.
“Ofglen” is not Emily’s personal name. It is a patronymic designation meaning she belongs to Commander Glen’s household, just as other Handmaids are called Ofwarren or Ofdaniel. When Emily is reassigned, another Handmaid takes the name Ofglen, which can make the character identity confusing.
Emily’s resistance work eventually exposes her to severe punishment. Gilead executes the Martha associated with her and subjects Emily to genital mutilation, while preserving her life because she is still considered reproductively valuable. The names Alma, Moira and Janine are also linked to resistance or rebellion, but they are not the Handmaid identified as Ofglen in this question.