This is not the only time they've played this game. There are many more scenarios and stories that Pearl has brought forward for Amethyst to act out. Amethyst never asks if the her requested performances are historical or fictional. She often wonders if this was really what Rose and Pearl's relationship was like, or merely what Pearl could only wish it was.
Amethyst sometimes suspects that Pearl is attempting to recreate fantasies that were never possible with Rose. Events and actions which never occurred between the two, but that Pearl longed for anyway. She wonders if some of the fantasies might be those which she wishes to share with the real Amethyst, but is too embarrassed to say so. It's a small inkling of hope that Amethyst dare not inquire about, for fear that it was not true.
They were both a bit delusional. They were both looking to gain something that neither could give. Pearl, longing for her departed friend, and perhaps lover, and Amethyst, wishing she could have had what Rose did. Neither is satisfied with the way things are, but their longing is so great that they'll keep trying. They'll keep playing games, continuing the charade, keeping up appearances.
The charade goes on for weeks. Any time she needs, Pearl calls on Amethyst. Amethyst is always there to oblige, even if she isn't happy about it. But she puts on a smile, for Pearl. She puts on whatever emotion Pearl chooses that day. She does anything and everything Pearl asks, to the best of her abilities.
She has already begun changing herself for Pearl, trying to show that she is different. She wants to be accepted by all the Crystal Gems, but most importantly Pearl. She tries to shrug off her childish and uncouth ways, to "grow up!" as Pearl calls it. She'd made her clothing symmetrical, trying appeal to Pearl's love of perfection. She wants to show Pearl that she can be different for her. She may not be Rose Quartz, but she can still love and fight and care just as hard.
Neither of them talk about their playtime outside of it. It seems they both share the same goal in not letting Garnet find out. It has crossed both their minds that she probably knows already, but if she's not saying anything about it, they won't bring it up. They've all been quiet and pensive when on missions. Steven carries the conversation, and they're glad for a break in the silence.
But the times when Pearl calls upon Amethyst seem to be getting more and more frequent, and it's really starting to wear on the purple gem. But she doesn't say anything, because she doesn't want to upset Pearl. She just wants to keep playing along, because at least then Pearl is paying attention to her. Amethyst can pretend that Pearl actually cares about her, and not just Rose.
Deep down, Amethyst knows that she'll never be good enough. She knows that she was born broken, born imperfect. Born a bad gem and a parasite. It was only through dumb luck, and the love of Rose Quartz, that she hadn't been destroyed the moment the Crystal Gems found her. If Pearl had had her way, that's what would have happened. Amethyst just knows it.
When things are held inside, someone is bound to break. Pearl isn't always happy with how Amethyst portrays Rose, but she keeps her mouth shut, trying to ignore how wrong she gets it, how much she doesn't understand what they had. And Amethyst, doing her best to ignore her feelings for Pearl, but whenever they're finished she retreats to her room and screams and throws things out of frustration.
And eventually, things do turn out badly. The false relationship that the two were attempting to maintain could in no way last forever. It was built on lies and deceptions and pretending. Pretending to like each other, pretending to get along, pretending to be something they were not. Bottled up emotions are never healthy, and eventually the pressure will cause a person to explode. The outcome is never appealing.