In a civil case, it is alleged Amanda Donaldson wrongly benefited from the credit card and by taking Harry Potter merchandise worth a total value of almost £24,000.
Under cross-examination, Ms Donaldson said all the spending was personal or business-related to Ms Rowling.
The author is pursuing damages in the case at Airdrie Sheriff Court which has been brought under her married name Joanne Murray.
Ms Donaldson, 35, was suspended and later dismissed in 2017 over the allegations.
Ms Rowling’s lawyer Kirsteen MacDonald queried transactions made by the former PA at gift shop Paper Tiger totalling more than £2,000.
Referring to one receipt showing the purchase of five chocolate bars and a Harris Tweed purse, Ms Donaldson told the court they were bought as a gift for a contact to “maintain Mrs Murray’s business relationship”.
Ms MacDonald said: “That is a strange combination (of purchases). It is ridiculous to suggest that’s what you would send to a business contact of Mrs Murray.
“Is it not the case here that you have again been caught out and this purchase was for you?”
The witness said: “Absolutely not.”
The former PA was also asked about the purchase of Halloween cards from Paper Tiger as well as chocolate letters spelling I,L and Y.
Ms Donaldson said they were bought for an ill child on behalf of Ms Rowling.
Ms MacDonald said: “I put it to you the letters stand for ‘I love you’ and were bought for you to give someone you were in a relationship with, or for your own child.”
Ms Donaldson denied the claim and said: “I recall the purchase as a whole but I don’t recall the particular letters.”
Another receipt from Marks & Spencer was also shown to the witness which included the purchase of a tin of shortbread.
Ms Donaldson said they were bought as a gift for staff at the Savoy Hotel in London when Ms Rowling had stayed.
The author’s lawyer asked if it was an appropriate gift for an upmarket hotel.
Ms Donaldson said: “They really appreciated it.”
She has also accused former colleagues and others of lying in the case.
Questioned about a £400 cash withdrawal from the credit card, she said it was given to staff at Castle Terrace restaurant in Edinburgh as a Christmas meal deposit, despite previous evidence that no deposit had been requested or deducted from the final bill.
Ms Rowling’s husband Neil Murray previously told the court Ms Donaldson had “faked” an email from the restaurant to pretend they had taken the deposit.
Ms Donaldson told the court the email was genuine.
Ms Rowling’s lawyer said: “On oath, you are saying that the manager of a Michelin-starred restaurant would lie to Mr Murray?”
The defendant replied: “I know what I did, so yes.”
The 35-year-old maintained that “all purchases were done for the business or while I was on business” when questioned about spending of more than £1,600 in Starbucks, with bank statements showing there were sometimes two purchases a day towards the end of her employment.
The final witness in the case, Colin Rowley, told the court he now employs Ms Donaldson as a PA and had found “no cause for concern” in her work.
Previously giving evidence in her defence, Ms Donaldson said she was never given specific instructions for the use of the company credit card and that her boss was often unapproachable and not to be disturbed while writing.
Ms Rowling has said she “does not accept” the claims made in court by her former personal assistant and took the unusual step of issuing a statement during the case.
The author said she had been left with no option but to raise the court action.
A statement issued on behalf of the author said: “Ms Rowling does not accept the position as stated by Amanda Donaldson in her evidence, and does not find that she has adequately explained her excessive spending on the business credit card or the missing items and cash.
“Before raising the court action, Ms Rowling and her husband gave Ms Donaldson every opportunity to explain the discrepancies in her credit card spending and the missing items and cash, but Ms Donaldson chose to deny any wrongdoing and instead to blame other members of Ms Rowling’s staff.
“During her evidence Ms Rowling explained to the court that she was left with no option but to raise the court action, in order to protect the reputation of her existing staff, and to ensure Ms Donaldson is not in the position to breach the trust of another employer.”
The civil case before Sheriff Derek O’Carroll continues in January.