Complex sentence: On January 21,1785, Jeanne told the Cardinal that Marie Antoinette wanted to buy the necklace, but, not wishing to purchase such an expensive item publicly during a time of need, the Queen wanted the Cardinal to act as a secret intermediary.
Split into simpler sentences: On January 21,1785, Jeanne mentioned to the Cardinal that Marie Antoinette wanted to buy the necklace. However, not wishing to publicly purchase such an expensive item on her own during a time of need, the Queen wanted the Cardinal to act as a secret intermediary.