Complex sentence: After a solitary use of "her" in an open letter, (misrepresented plurally as "pronouns") she prefers feminine pronouns but has since opted to use male pronouns when referring to Matt in the past tense.
Split into simpler sentences: After a solitary use of "her" in an open letter, (misrepresented plurally as "pronouns") she prefers feminine pronouns. She has used male pronouns when referring to Matt in the past tense.