The money was to buy a new tv unit which she chose and bought in argos. Would the fact that it was paid on my card help in any way?
If you bought the unit and it was on your card then you are the owner of it, which does change things slightly, as now you can prove that the transaction actually took place.
If you never want to speak to here again what you could do is to go to her house with a friend and ask the police to attend, to prevent a breach of the peace, they wont help you, and collect your goods (make sure you have the receipt).
She will either let you take it (which is better than you have now), scream out that she'll pay you back (in which case you now have witnesses to the debt), or say that it's not yours (in which case you can then say, in front of the police, that the Argos cctv
will show her with you when you bought it).
Things can get tricky, but don't go down on your own and make sure you get the police to attend as when you have asked her about it before she has been "threatening", and all you want them there for is to prevent a breach of the peace.
Depends how far you want to go, you could get a solicitors letter sent to her and see if that spurs her on to pay you back,