I advertised it on a social network site and the lady that came roundand tried it out and ummed and arred about it and I said that she should go away and think about it and come back if she still wanted it.
She said (each time I said this) that she would donate it to a charity she is involved in if she didn't get on with it.
We agreed on a price and that my OH would deliver it the same evening.
He delivered it and she paid by cheque (which I have cashed) and again said to my OH that she would donate it if she didn't get on with it.
While I was away on holiday she came round and left a note saying that she couldn't get on with it and she wants to return it.
Do I have to take it back?
I wouldn't have minded but she kept saying she would donate it if she didn't want it even after I said to think about it!!!
No, you don't have to take it back. The only requirement under the Sales of Goods Act that applies to a private sale is that the item must be as described.
As she came to view it, tried it out, thought about and bought it she has accepted it.
She is perfectly entitled to return it if she so desires, but you are under no obligation to refund any monies providing, as has been stated above, that it was of merchandisable quality. Let her bring it back, give her nothing and sell it on again!