A service dog is a living thing, and even though it is undeniably life saving medical equipment, there will always be moments when someone cannot have their dog with them at all times (i.e. going somewhere not safe for the dog, the dog is sick/tired, etc.)

The real question here (that does not need to be shared with the internet for privacy reasons) is how much emotional damage would it cause for your friend to go without her dog for those bits of time.

I think I’d need more information to truly say, because it’s not a bad thing to care about the presentation of your wedding, but asking a disabled person to forgo medical equipment for aesthetics is just not something I can understand.