Option A. Its what the bride and groom want and it has nothing to do with the mother (unless she is paying?)
Absolutely option A. Didn't even have to think about it
Seriously, is this genuine as it seems very convoluted. Anyway need i spell it out..it's the bride and groom's wedding, no one elses and with all weddings you cannot make everyone happy, someone will always be hacked off about something.
Tell your friend to do what she wants, if it was me I would go with option A. The mother needs reminding that it is not her day.
Only the bride n groom know the full story behind each issue, and only they know which person is more important to have at there wedding, so other pple's opinions don't matter. Its nobody else's business outside the immediate family.... what does it even have to do with u?