JOQ: You can do exactly what you've said.
Your friend needs to understand that, at least in the United States, credit cards and cash are interchangeable in virtually any situation you can think of if the business accepts credit.
Most restaurants are set up such that each seat at a table can be billed separately, and easily, if the server puts in the orders by seat. It makes it a cinch when you've got a table of ten that, at the end, says we all want separate checks. I always put orders in by seat when I had large parties so that I could split the check this way when the group didn't want to "divide the whole check by ten." Now, if you haven't done "by seat" ordering and a table requests separate checks after the fact if you've got more than say, four people, what you generally do is offer to divide the total evenly and let the folks at the table "swap additions/subtractions" to their particular bill if someone ordered far more/less than another. Trying to do accurate "by seat" stuff after the fact, unless you have a perfect memory and are really proficient at moving items, is a nightmare.
An even division of the check simply involves running as many credit cards as you're handed for the appropriate amount.
Credit cards and cash are, for all practical intents and purposes, interchangeable. [You can substitute debit card for credit card as needed. It's just electronic currency rather than paper.]