That’s a tough one. I don’t own a business, but here are just a few thoughts I had, if I can humbly share them with you. If people know you did the cake, they could mistakenly think you did the cupcakes too, which could be a problem if they turn out crappy! On the other hand there’s the whole “It’s her wedding and she can do what she wants.” point. Is there any way to see what the family member’s work looks like or a way to put out a little sign that says “Cake by…Cupcakes by…” Would she possibly be willing to do a cupcake tower and then have your cake on a separate pedestal stand. Maybe if you showed her photos of some awesome Amy Atlas desert tables she’d like that idea & you could still do the signs if needed.
Hope you figure it out. I’m sure others with much more experience and wisdom on this subject will have more to say.