Four weeks in Fiji too much?

I plan to go to Fiji in June/July and would like to stay for four weeks. Is this too long? I would definitely like to learn a little bit about the local culture, BUT I must admit I am mainly interested in beaching, relaxing, seeing beautiful scenery, island trips, snorkeling, partying etc. I'm a young girl traveling by myself for the first time, so I guess that's why I'm especially afraid of getting bored. Are there plenty of hostels where it's easy to meet people? Should I consider doing 1 or 2 of the weeks in New Caledonia and/or Vanuatu?

Thanks for any help :)

PS. This might be a hard question to answer, but would I survive four weeks in Fiji (living low/lower mid-range) with around 3-4000 US dollars pocket money?

Barely enough time to hit the highlights IMO.

One week Kadavu, one week Taveuni, one week Ovalau, one week Yasawas and you'll barely scratch the surface.

That's lotsa cash you'll have a fine time.

4 weeks is not much in fiji, for the non resort turist!
3-4000 thousand US, with the new exchange rate since yesterdays devaluation, you will live like a king here...

Is this too long? I'm especially afraid of getting bored.

Maybe - it'll depend on you. Other people can't answer this question for you. If you haven't done so already, read a guidebook. Anyway, there's no point in spending money getting to another island in a different island group when there are enough different islands within Fiji to visit. It is easy enough to make a list of places in Fiji to visit for a 1 week trip, or 2 weeks, or 2 months .. or longer.

I stayed 2 months and couldn't manage half of what I might have done. Of course, I also got addicted to swinging in a hammock - you'd be amazed at how fast the time goes by even when you're not doing much.

Are there plenty of hostels where it's easy to meet people?

No, there are not plenty of hostels, probably none. However, there are many so-called backpacker resorts which serve the same function.

would I survive four weeks in Fiji (living low/lower mid-range) with around 3-4000 US dollars pocket money?

Considering that budget end is/was roughly around US$40 a day, you will survive.

I've met people they wanted to stay 2 days in Fiji - they stayed 2 weeks. Others wanted to stay 3 weeks - they stayed 3 months, and others again who wanted to stay 4 months and stayed for ever! I also met people who wanted to leave the country as earliest as possible.
What do you want??? If staying for example in Sheraton you will be bored and your money is gone pretty soon.... consider an island stay - nothing like luxury - away from the main tourist path, with a bit of luck you find a friend for your live. Oh, I just see that you are a girl - well special rules apply: 90% of un married Fijian man look for a European wife - so be careful if you don't have that kind of intentions. Now don't get put off with that - tell them straight away , that you are NOT interested and it will be accepted. If you will give an interested Fijian man any hint of hope he will keep trying.
Now, I just worked it out with new exchange rate: 3000 US $$$ staying at Caqalai - a basic Resort which is still "un-touristy- will give you a hundred days of single bure accommodation plus meals and a bit of extras, like side trips or snorkelling trips.

If staying a longer time on Caqalai ask them to introduce you to the GAP girls ( british or Australian volonteers working in villages) on Motoriki - they are probably your age . For hiking come to Levuka - silana or bobo's Farm offers this.
Party??? Again, what do you expect?
You just need to find the right crowd to get drunk: the European way? the Fijian way? Sorry to be sarcastic about this but I have witnessed to many "parties" on either side. Opportunities for that are everywhere! Neither way I like to be too public about that. If you want to get more specific about that then send me a pm

Bottom line - you can thoroughly enjoy Fiji in 4 weeks and find out, that it was not enough if you've found the right place for you - the right people and the right time to be there.