Who cares knows?
Don't know, but is she is, with who should she be?
We don't know at all about her sexual orientation and we don't give a ****, it has absolutely no importance in the story. Tho, I've always pictured her with Zeke, I think that as a couple (without secrets or lies) they could have been great together. And every time they agree on something, Zeke would be like "As expected of you! That's exactly right!"
I think some people think of her as having an interest at least towards women (doesn't exclude an interest towards men) because of chapter 105, when she talks about Yelena and how she admired her, as being a heavy supporter of Zeke. Tho, I interpreted like if Pieck also had a great interest in Zeke too (A bit like too fangirls talking about their favorite singer, however, I don't want to reduce Yelene or Pieck to the state of "fangirls")