Wait wait, are they actually together?
Nope, Miyoshi is talking to Ayano the way you talk to your bff. In Japan, at least.
For a Japanese person, talking like that to somebody you're actually dating would be completely out of the question. Too embarrassing. But if your bestie calls you in the middle of the night, bawling about a dream where you didn't like her anymore, it's a-okay to swear eternal love to her and promise to make her your wife.
Also what was happening in the last page, I don’t really get it?
My educated guess is that Miyoshi couldn't go back to sleep after Ayano's call; so, lacking anything better to do, she called Ai and asked her if she would do for Chie all the things Miyoshi had claimed she would do for Ayano. And I'm guessing Ai said she wouldn't want to share a grave with Chie—prompting Miyoshi to immediately call Chie and rat out Ai as a fickle and disloyal lover. Lol, poor Ai. (⁀ ᗢ⁀)