I also just realized, you can tell whose hand is whose by their armbands: blonde girl has them on her wrists, black-haired girl has them on her elbows.
I'm with "DatYuriAddict" here. I think their relationship is usually healthy, a lot of people have some jealousy in relationships as it's a pretty human emotion, the key is to talk about it and use that communication to sort out their feelings together.