and not having a go, but you should sort all that out before the deal is done. Not sure what the dept of fair trading would say, they may be able to help..

 You are out of luck getting a key from previous owner Im afraid. You bought the car as is with one key. Unless you saw there were two keys when agreed to buy it there isnt much you can do.

There are guys that advertise on Gumtree that can do aftermarket replacement keys for a fraction of the cost i.e around $200. I looked into it but the Mrs spare key ended up turning up in her coat pocket after months of blaming me for losing it. Had a bloody field day with that one 

You have zero chance of Consumer Protection getting involved in a dispute regarding a component of the vehicle that doesn't affect its function and I doubt they'd get involved in a private transaction in any case and really are a toothless tiger when dealing with genuine issues with stores. Doesn't mean that you can't put the wind up her and give her notice that you will be taking it up with Consumer Protection in 14 days time if you do not hear back from her.

I'd personally have taken the offer of half of the purchase price which would have reduced your stamp duty as well.

I believe in the eyes of the law the cars is sold as seen. Unless you have paperwork or and advert that specifically stated that 2 keys were provided, you bought and exchanged on what you saw/got.

I had a mate that bought a repaired written-off car once, the seller didn't tell him, but he didn't ask or do a revs check. No comeback on the seller. My mate actually went around there in a bit of a rage and the guy claimed he didn't know?!?! Nothing my mate could do other than get himself arrested if he wanted to be a fool.

The fact that she said she would get you a key is dishonest, but the reality is she would never have been able to get a key made as A) not as the legal owner or B) she wasn't in possession of the other/only key.

In the end it's Buyer Beware.

You were presented with what was for sale. If the hidden spare wheel was missing or carpets that were part of the original sale of the car were missing, you can't complain if you find out afterwards. 

Given you said she initially said she would go halves and then you 'insisted' she pay the full amount, perhaps she felt threatened and agreed just to end the conversation.

If you were genuinely unhappy then you should have cancelled the transaction on the spot and advised your bank it was a scam and they should reverse the transaction/cancel payment/whatever.

Did you haggle any money off the advertised price?

Unfortunately every one above is correct unless you stated in the contract 2 keys or photo of two keys advertised the sale is "as is"

Same happened to me. I got my spare key from a locksmith in Morley. A1 locksmiths. they were pretty much the only one who could do it and was a reasonable cost.....from memory $600 from dealer ...and think it was $250ish from A1
Locksmiths

Edit : as for rocking up at her house. be careful. Im sure you could talk with her politely and ask for some reimbursement but it's a fine line between that and harassment. If I was you I would get a quote from a locksmith leave a polite message asking her for full or even half and hope she is reasonable.

Edit number 2: just thought I'd mention that when A1 locksmiths did my spare they code it with the original I have so that only those 2 work on the car and any other key out there will be useless.

 Same scenario about the seller losing the key when I bought a vehicle recently. I kept the amount of a receplacement key after getting a quote from Hyaundi with the proviso that if the seller found it, I would then pay the amount to them. Low and behold, 6 weeks later they found the key and we did the exchange. Admittedly I did do a test of the key before the money exchanged hands. I'm a suspecious bastard. Doesnt help your situation but may give you some ideas if ever in this situation again. 

 i just realised i just traded in me old car and only gave em one key who knows where the spare is haha but with anything mate boats cars etc it everything should be put in the contract  and both sides be happy before the buy

but the people who are selling you the boat/car are always out to get the most and give the less so always be wary of that never rush and always sleep on it for a few days its suprising how much things you remember to ask before its to late.

 Yeah gonna have to suck it up she’s under no obligation ..should’ve nailed that prior to sealing the deal . Car dealers $500 tell them impregnate themselves . I’d be keeping on her good side she may find the spare and if you hassle her you might get one of those Restraining orders ..  

A contract requires consideration. The deal for the car was done for the consideration (amount you paid) prior to what effectively was a second contract for the second key, where the seller got nothing for the commitment to give the key and hence there is no contract.

Only hope is she does the righty and pays at least half.

Harsh as it is but I reckon if the buyer hasnt asked and the seller isnt lying, you gotta wear it.

 Bought a 40 grand low km Pajero a few years back from reputable dealer, when picked up asked where is the spare key, sorry mate isn't one was the reply, told them wasn't moving until a spare key appeared, long story short I received a key but still cost me a hundred or so by the time it would start the vehicle .

 Thanks everyone for their reply.

 Lesson learned.

 Z00m, no, price was reduced from advertised price already before I agree to buy. I should have done that but I didn't know the price of getting an after market key. Had I known, I would have done so.

 Should have held off the transaction on the spot when she told me she lost the spare key.

 is never rush things i guess