Teri: You still have it Wrong. That is Too Many Entries.
1a. Enter Credit Card Charge by Company A, as Other Asset.
1b. Enter Credit Card Credit when they learn Company B repaid it directly to AMEX, posting the expense entry as Other Asset.
Company B:
Post a Payment to AMEX posting what was bought on their behalf.
Or, Company B will want to use Enter Bill, as I showd, to enter the Real Vendor name, ending at $0 on the bill, because it was offset to a Liability account. In this example, the Check to AMEX is paying out that Liablity balance.
