This is adorable! I'm not sure if I'm right here, but, is that one of the cute anthropomorphic stars from the original Care Bears cartoons? Rarity looks very happy indeed - love the hair and expression! Your colours are always so lovely too.
It looks like Rarity suddenly realizes it's a lot more fun to play with the stars than to become a star herself. It's great to see her having some wild and untamed fun (even if it means her mane and tail are untamed for a while too). I hope the joy and excitement last her a good long time, and I think the little astral object was very happy to accommodate her trip. It's a great way to bring about lots of smiles for everyone.