Jasmin and Rosie are close friends so are My Belle and Rosie. This is obvious. Theirs are different kinds of friendships. With Belle and Rosie they just love a laugh, a bit of mischief and to talk until the end of time, the Jasmin and Rosie relationship feels more like Kristy and Kami and is built around being totally comfortable and at ease with each other. Rosie does seem to divide her time equally between the 2 as she did on her last trip. She is very close friends with both.
The Jasmin and Belle relationship is not so close. They do spend time together but it is mainly, jogging, exercising, shopping or talking about beauty products. I am not so sure they would be friends without Rosie (and Caro). If you notice Belle's friend Blair has now become much closer to Jasmin than Jasmin seems to Belle. Again this may be to do with Jasmin and Blair being similar like Rosie and Belle are similar.
My ExcitaBelle's energy and liveliness is just amazing. Rosie is her perfect companion and vice versa and of course they are going to have an effect on those around them.