Not really - I understand warranty with Apple will be sent to authorised service centres (and can be any of them), unless you take up the retailer’s extra warranties (theft, screen break) which is retailer specific. Further, if you’re taking Apple Care (and not the retailer specific programs), this shouldn’t be an issue.

Do you mean that she has previously edited her videos just fine on a 10 year old MBP? In which case, the highest end would definitely be overkill. I would suggest a 15 inch MBP for portability. Max up on the RAM if possible for future proofing.