I just read this whole thing. You handled it exactly how I would have...and did.
Let us know what happened when you delivered the cake...if the mother had complaints, ok? Good luck and I'll cross my fingers for ya.
My only bridezilla story was this.....sorry, it's long!!!!
Last year I had a bride that came in January to look at my cakes for a wedding in August. I sat with her and her fiance for over 2 hours and they didn't book but they thought they wanted me so we did up the contract and they signed everything. I said I would hold it for payment unless someone else had money to book their date and then they would get first choice. The bride said she needed to get the money from her mother. At this point they were not exactly sure of the final details of the cake and I told them they could wait until 4 weeks before the wedding to make a final decision. A few weeks later, they told me her mother would be paying for the cake and she would be sending me a check to book the date (1/2 the total cost). A month later I finally received the check and booked their date. 6 weeks before the wedding I sent out the normal invoice to the bride (and a copy to her mother since she said her mother was going to pay) to show they needed to make their final design decisions 30 days before and the balance of the cake (1/2 the total cost) would be due on so-and-so date (two weeks before the wedding). The gave me the final design a couple days after the 30 days deadline and I let that go...no biggie. For some reason, I knew I was going to have trouble getting the money, so about 5 days before the balance was due, I emailed a reminder to the bride AND her mother, just to cover all bases. On the day the balance was due, I said to my husband, that I bet I'd have to call them when I don't receive the money in the mail. The mother ended up calling me that day before the mail came and told me she would be sending out a check for the balance in two days (the following Monday). I told her she needed to pay the balance by midnight, not two days later, as per the contract or I could cancel at my discretion and they would not get their deposit back. She got upset and said....I don't understand why you can't get the money two days late. I told her that was fine as long as she understood that if that was ok, then I felt it was ok to deliver the wedding cake two days late. She ended up driving 1 1/2 hours her to deliver the check. Of course she dropped it in the mailbox and did not come to my door. She then went home and emailed me to tell me to let her know that I received the check. When I delivered the cake two weeks later, her driveway was a one-lane deep rutted path uphill with a little turn around loop at the top. I was the seventh car in the driveway, and in order to get the cake to the reception area, I had to walk past 6 cars, up a narrow driveway, then across the front yard, around the patio to the back yard, across the back yard, down a narrow footpath filled in with baseball sized limestone rocks and then across a field about 50 yards to a tent. I couldn't believe it!!!! Luckily, a couple of the groomsmen offered to help me carry the tiers. I didn't want them to help with them being in tuxes already but they insisted. Then when I left, all 6 cars in front of me had to go back out the driveway, let me out, and then reenter the driveway. I guess everyone that came to that wedding was held captive until everyone left the wedding? Oh...and they had port-o-johns beside the tent, about 10 feet from the food. Now you KNOW that bride was using a port-o-john!!!