That is true, Chauveau Lagarde and Tronson Ducoudray were assigned just before the trial opened. Chauveau Lagarde wrote about it : he was away in the country and had to get back to Paris at once. They both met Marie Antoinette in her cell and told her to ask for a few days more so that they could examine the charges. She first refused to ask those men who condamned the king, her husband, but her lawyers insisted, reminding her of her children, who needed their mother. So, the queen accepted and sent a letter. Her request was not accepted.
Indeed, Marie Antoinette's replies are very short and clever. The most famous one his her indignation when accused of incest : "I did not answer because nature refuses to answer such an inculpation made to a mother ! And I appeal ot all those (mothers) who could be here !". Even the terrible knitters were moved and felt solidare.
A less known reply is about a paper she was accused to have written for money. She asked when it was written. On August 10th, they said. Then, she replied it was impossible, for, on August 10th, she and her family went to the Assembly at 8 in the morning. How could she make a paper for money when she was imprisonned in the logographe cage ! See how sensible, present and clever she was, even so tired !
Then, there are her replies when questionned a few days before her trial. They tried to trap her with questions about royalty and republic, so that she would declare she was a royalist. She never said so, replying that all that mattered for her was the happiness of her son and of the French people, with or without a king.
When they told her that she and her husband would get back on the throne at any cost, even speading the blood of the patriots, she quietly replied : "We did not have to get back on the throne, we were on it". How clever and witty !