They need to just give her the $14k immediately and then eat it if it's a problem. Stop processing the transactions going forward or until it's sorted out, but do not steal her money. Also, I found this distasteful: "I want to clarify that Square is not experiencing a technical glitch. While I cannot speak with you about Monica's individual case, I can tell you that Square's Customer Success team spoke with Monica ye…
If the question is legal liability for violating sanctions, releasing the $14K could put them on the hook for much more than $14K in liability.
If they aren't able to do that then maybe this company should not be operating in Canada in the first place.
[edit: oops, I meant Square not Stripe!]