Zoro lost his duel with Mihawk, which resulted in him getting hurt badly.

Zeff treated his wounds. He wasn't awake the entire time, and he got settled in Nami's bed.

Sanji asked you to look after Zoro for some time since you're a nurse, when you weren't working you'd clean Zeff's kitchen.

The crew was thankful to have you there but you understood they weren't doing good since their friend was on the verge of death.

You didn't know the Straw Hats well but offered to help them