Trustworthy x Trustful: Qual é a diferença

Hello Guys! My student said to me someone is 'trustful' because you can trust them; I corrected her saying 'trustworthy'. After the classe though, I started wondering if there was such thing as 'trustful' and found this on Merriam-webster:

"having or showing trust in another <a trustful child quietly sleeping, sure in the knowledge that his parents would be there when he woke>
related words - gullible, innocent, naive"

But on several forums I found people saying they were interchangeable, which reading this definition, I think they're not.
What are your thoughts on the matter?
Thanks in advance!