Sisters engaging in sexual play -( please read thoroughly)

Someone I'm intimately bonded with confessed to me that she always played sexual games with her sister when they were ages 9 - 12 and she felt ashamed because it didn't seem normal. They shared a room and bed, and would play make-believe until they got to a sex-scene where one sat on the other in missionary position and both stimulated their cl*toris by rubbing against each other (with clothes on). She says that she would picture her sister as the male (Harry Potter and she was Ginny) and her sister would do the same, and that she would just let her mind go blank and only pay attention to the pleasure because she did not want to look at her sister.

Please note that they did not touch each other with their hand, did not take their clothes off, or anything like that. They simply rubbed their vaginas against the other while fully clothed in order to stimulate their cl*toris. They would not plan these sex scenes prior to the game, it would just go into one. For example, one characted would kiss the other (they just put their cheeks against each other to kiss) and then they would "have sex."

Is this normal for girls that share a room and bed?