Fiji - one week on a budget, what to do/where to go etc

Hi, hoping someone can give me a bit of advice. My sister is arriving in Fiji for a week on the back of a trip round the world. She flies into Nadi for a week - she'll have quite a tight budget - I know Nadi isn't really worth sticking around & that the islands are much nicer to visit, but can anyone recommend an island/accomodation that would be safe/cheap for a girl travelling on her own. I'd really appreciate any help/tips as just trying to get something booked asap. Thanks so much in advance for any help!

Each of the islands Ive been on (and I guess that the ones that I havent been to) are all "safe for a girl travelling on her own." -

I wouldnt call Isalnd living particularly cheap - certainly they are dearer than , say Asian islands

What is her budget?

Octopus resort on Waya. She could stay in the dorm.

Thanks Tilos & Mandja - her budget would be about £20 a night tops ($30). Did you visit the islands such as Beachcomber from Octopus?

I did see Beachcomber from onboard the Yasawa Flyer - it looked small.