So in the BNHA show, we know Ms.Joke always ask Azaiwa to marry her and etc.

So what if she does that because she's into girls and she knows Azaiwa is into guys.

So Azaiwa and her have the inside joke of marrying each other because of that.

Also I feel like Azaiwa and Ms.Joke found out their sexuality because when they dated they felt awkward so they stayed as friends and have the "marry me" joke