You can do this! It must feel like a big moutain for you now, but you can climb this mountain and get to the other side! You´re such a sweet person and I´m sure that your sister long for you! She´s gonna love having you there!
If you need some time alone, just tell her that and be by yourself to think for a while. She will understand.
As for your eating... I know that you´re having a hard time eating, but my dear friend I and everyone else here loves you and don´t want you to disappear! Try to see food as a friend, a friend that makes you live and that makes it able for you to use your wonderful voice singing! You love to sing, right?! Food gives you energy to fight the OCD! You´re such a good fighter, but let the food help you gain even more power! Buy the food you like and eat slowly, feel how it´s doing good for you, my dear friend.

I have faith in you!
Let´s fight the OCD together!

Hugs
Nina