Rude & Demanding clients

Hi all! I am new to the business of making cakes for other people as my own business and not at a bakery. Up to this point (two years into it) I have never had an unhappy client. A woman got a quote from me for a 3 tiered wedding cake. She didn’t like the quote, and insisted she only spend $XXX for the wedding cake (less than half of what all the bakers around here would charge). I told her I was sorry but that I couldn’t do what she wanted for the price she wanted. Fast forward HOURS of back and forth “quoting”. She comes in for a cake tasting. (At my home since I am a cottage baker and she knows this.) I give her 4 6” single layer cakes for $25, let her box up the leftovers since neither bride nor groom could come. I did a TWO HOUR consultation at that time, due to her situation I agreed to do a small (10”) grooms cake & extra top tier for FREE, and she said she “would get back with me”. Two weeks later she decided she wanted to book my services. (Probably because it was a killer steal @ approx 1.80/serving instead of $3+ like in my area). I told her the contract would be due as well as the deposit (50%) before I could guarantee her spot. She made me send her another quote plus the contract and still messaged me a good hours worth after that. She then asked if she could pay the invoice for the deposit in 4 weeks which would be 2 weeks before wedding. I said sure but no guarantee I’ll have room for you. So, she paid the deposit. Due to covid (and she knew about covid when she paid deposit since it was after the pandemic started) the wedding was postponed. So I told her I would transfer her deposit to the new wedding day. Just two weeks before the wedding day and after I had already taken on other clients because she canceled the original date she tells me the wedding is back on just at a new location and smaller and that the big wedding would happen later. So, she wanted to know if I would make her a smaller two tiered wedding cake instead of the grooms cake (the free 10” i was doing for her). I politely told her no. So she then got a quote for a 2 tiered cake and then a 3 tiered cake and went with the 3 tiered cake. I didn’t get a confirmation of time until 4 days prior to event and the night before the event she changed the time. I text her a picture of the finished cake the morning of the event. She said she didn’t like the blue color and requested me to change it. I explained I couldn’t scrape the cake as I didn’t have time and if I altered it that it could compromise the integrity of the cake as cakes are delicate and cannot handle pushing and moving it a lot. I show up to the location 15 mins early due to her changing the time (though I thought I was right on time because she kept confusing me on correct time) the cake was received by the bride and was set up and intact. 6 hours later I get a text saying “I’m sorry your cake fell. This is what I had to do. It almost fell over the banister and her mom won’t quit talking about it.” I’m not sure what she meant by my cake fell and by the pictures given I had assumed someone dropped, knocked, etc the cake over. Roses had been taken off the cake, and other items added to the cake. The cake has been moved From original location as well. I told her I empathized with her situation but per our contract that I am not responsible for any damages done to the cake after set up. I never heard back from her. The next night her nephew left a horrible and untruthful negative review on my Facebook. The next morning I decided to refund her 100% of her deposit for the bigger wedding and wished her well as “I didn’t think we were a good fit for each other”. I refused to refund her for the cake she messed up and consumed. What would you have done? What should I do differently going forward for other clients?

Here’s a link to show the picture for inspiration although she changed the flowers to roses and fresh baby’s breath dusted in navy blue, and the middle tier to have White and navy blue on it. Then to show what I showed her, what it looked like after she asked me to alter it, and what she txt me after “the cake fell”.
https://www.instagram.com/p/CANfjK0lGhV/?igshid=hi0hay1sfuoe