All you need to do, is trade at least one Ancient Beastcoin to Sagheera (you can usually find them on bazaars). Then talk to Monisette. After that, Monisette should accept the materials from you, as long as you have the right pieces.
so I figured it out I had to select "just want to chat" when speaking to Sagheera then ask about the piece I wanted to upgrade then he let me give him the coin. Trade with Monisette worked immediately after.