Another requirement not explicitly said is the bot needs to like you a certain amount. Annoying because there's no exact way of telling how much progress you made yes, but you know just pet her, make the love to her or play and that should make a unique dialogue when talking with her appear
Uff, you've got me blank with that one. I play the PC version so I won't be of help on that, really sorry. As far as I know the mobile is not as polished as the PC so it could always be a bug I suppose