Natalie McGarry, 40, said that it now seems "naive" that she did not keep receipts for everything associated with one of the events she was involved in.
McGarry, who represented Glasgow East, allegedly embezzled £21,000 while she was treasurer for Women for Independence (WFI) between April 26 2013 and November 30 2015.
A second charge alleges she took £4,661 between April 9 2014 and August 10 2015 when she was treasurer, secretary and convenor of the Glasgow Regional Association (GRA) of the SNP.
McGarry, who is on trial at Glasgow Sheriff Court, denies both charges.
Defence agent, Allan Macleod, took Ms McGarry through her reconstruction of events she attended in 2014 which includes notes of the costs incurred.
Jurors heard that she attended and spoke at events around Scotland in her WFI role, including taking part in broadcast interviews and appearances.
In February 2014, she was involved in organising the filming of a Women for Independence video to tie in with international women's day in March, which featured 20 women including actress and comedian, Elaine C Smith.
Filming took place at the Pearce Institute in Glasgow and expenses for the day included room hire and catering, which consisted of drinks and snacks bought from local shops.
Mr Macleod said: "There were a lot of expenses there that you have been unable to quantify with any degree of certainty."
Ms McGarry replied: "Yes, it seems naive now to say, but it didn't seem like something we would be keeping receipts for, it was local shops and making sure women who had travelled from all over the country were taken care of."
The court also heard that she attended a Yes in the Park event at Strathclyde Park in Lanarkshire in June 2014, for which she and other activists had to buy a gazebo and procure a helium tank and balloons, while face-painting was to be on offer.
Ms McGarry said: "In a previous life, I was an entertainer at McDonald's so I had some residual face-painting skills so I had said I can do face-painting.
"I don't remember how I did get that helium tank to Strathclyde Park but we did manage."
The court heard that only records of things that cost over £200 had to be kept for the Electoral Commission.
Mr Macleod said: "You don't have any expenses down for Yes in the Park and you told us you can't remember how you got there.
"In addition to travel expenses, can you say there would have been others?"
Ms McGarry replied: "Yes there would have been others but none were over £200."
McGarry was elected as the SNP MP for Glasgow East in 2015, but later served as an independent MP. She did not contest the seat in the 2017 General Election.
The trial, before Sheriff Tom Hughes, continues.