Attribution of miracles to the Saints

First post here. Posted in r/AskAPriest, and mod advised posting the question here, since it's a theology question. Here's the question.

How are miracles attributed to saints during the canonization process? A protestant coworker asked me something to the effect of, "If you pray to a saint for intercession, and you ask me to pray for you, how does the Church know that it was the saint's intercession and not my intercessory prayer directly to God that the Miracle is attributable to?"

I have not thought about this before, and I am too amateur of a theologian to provide a solid answer.

Thank you in advance for your time, thoughts, and answers.