Liam Nolan of CBR.com has the story:
Passages from Claudia Gray’s Leia: Princess of Alderaan novel imply that the Resistance’s Vice Admiral Amilyn Holdo, played by Laura Dern in Star Wars: The Last Jedi, may be either bisexual or pansexual.
The hint that Holdo may not be straight comes during a conversation with Leia about the possibility of an interspecies relationship:
“A pair of pretty dark eyes.” Then Amilyn thought about that for a moment. “Or more than a pair, if you’re into Grans. Or Aqualish, or Talz. Or even – ”
“That’s all right! Leia said through laughter. “It’s just humanoid males for me.”
“Really? That feels so limiting.”
“Thank goodness it’s a big galaxy.”
Although the passage doesn’t explicitly state that Holdo is bisexual or pansexual, it notes she’s interested in more than just humanoid men. While there are many alien species in the Star Warsuniverse that are both humanoid and non-humanoid, some don’t fall into a strict gender binary. The insectoid Xi’Dec, for example, have more than 180 different sexes. Other species are hermaphroditic or have a third sex.