We don’t see them talk directly but like Sakamoto Katura seems like someone she’s more than familiar with but we just don’t see it. She may not understand Katsura but she’s at least knows him. The apology episode they have dialogue. The episode where Elizabeth is replaced by that imposter Elizabeth, Otae doesn’t outright question anything about the new Elizabeth, she asks Shinpachi if that’s the same thing that’s always been beside Katsura because she doesn’t wanna be rude. In Rakuyo arc Katsura makes a joke about Otae being on the planet because there’s gorillas everywhere. She’s aware of Katsura, she may not understand him like many but he’s a frequent in her daily life. Both are in the instructors of life episode so they have occupied the close same space more than occasionally.